Fundamentals of Physics and Chemistry Important to Microbiology

Billions of years of chemical evolution on our planet have created a chemical library of immense size and diversity – the Earth’s chemome. Scientists at Stanford are leading research directed at translating the library, creating fundamentally new knowledge about the origins and workings of life, and how molecules, molecular assemblies and metabolic pathways contribute to the chemistry and biology of living organisms. From the structure and function of molecules within a cell to the interaction of cells within an organism and inter-organismal biochemistry, the research is providing new insights into normal and abnormal biological function, and with that, new strategies for the prevention, detection and treatment of diseases.

Like all other matter, the matter that comprises microorganisms is governed by the laws of chemistry and physics. The chemical and physical properties of microbial pathogens—both cellular and acellular—dictate their habitat, control their metabolic processes, and determine how they interact with the human body. This appendix provides a review of some of the fundamental principles of chemistry and physics that are essential to an understanding of microbiology—especially Microbial Biochemistry and Microbial Metabolism—assume that the reader already has an understanding of the concepts reviewed here. Life is made up of matter. Matter occupies space and has mass. All matter is composed of atoms. All atoms contain protons, electrons, and neutrons. The only exception is hydrogen (H), which is made of one proton and one electron. Elements have unique physical and chemical properties and are substances that cannot easily be transformed either physically or chemically into other substances. A total of 118 different elements (92 of which occur naturally) have been identified and organized into the periodic table of elements. Of the naturally occurring elements, fewer than 30 are found in organisms on Earth, and four of those (C, H, O, and N) make up approximately 96% of the mass of an organism. Each unique element is identified by the number of protons in its atomic nucleus. Many elements have several isotopes with one or two commonly occurring isotopes in nature. For example, carbon-12 (12C), the most common isotope of carbon (98.6% of all C found on Earth), contains six protons and six neutrons. Heavy isotopes and radioisotopes of carbon and other elements have proven to be useful in research, industry, and medicine.

Energy

Thermodynamics refers to the study of energy and energy transfer involving physical matter. Matter participating in a particular case of energy transfer is called a system, and everything outside of that matter is called the surroundings. There are two types of systems: open and closed. In an open system, energy can be exchanged with its surroundings. A closed system cannot exchange energy with its surroundings. Biological organisms are open systems. Energy is exchanged between them and their surroundings as they use energy from the sun to perform photosynthesis or consume energy-storing molecules and release energy to the environment by doing work and releasing heat. Like all things in the physical world, energy is subject to physical laws. In general, energy is defined as the ability to do work, or to create some kind of change. Energy exists in different forms. For example, electrical energy, light energy, and heat energy are all different types of energy. The first law of thermodynamics, often referred to as the law of conservation of energy, states that the total amount of energy in the universe is constant and conserved. Energy exists in many different forms. According to the first law of thermodynamics, energy may be transferred from place to place or transformed into different forms, but it cannot be created or destroyed.

The challenge for all living organisms is to obtain energy from their surroundings in forms that they can transfer or transform into usable energy to do work. Microorganisms have evolved to meet this challenge. Chemical energy stored within organic molecules such as sugars and fats is transferred and transformed through a series of cellular chemical reactions into energy within molecules of ATP. Energy in ATP molecules is easily accessible to do work. Examples of the types of work that cells need to do include building complex molecules, transporting materials, powering the motion of cilia or flagella, and contracting muscle fibers to create movement.

A microorganism’s primary tasks of obtaining, transforming, and using energy to do work may seem simple. However, the second law of thermodynamics explains why these tasks are more difficult than they appear. All energy transfers and transformations are never completely efficient. In every energy transfer, some amount of energy is lost in a form that is unusable. In most cases, this form is heat energy. Thermodynamically, heat energy is defined as the energy transferred from one system to another that is not work. For example, some energy is lost as heat energy during cellular metabolic reactions. The more energy that is lost by a system to its surroundings, the less ordered and more random the system is. Scientists refer to the measure of randomness or disorder within a system as entropy. High entropy means high disorder and low energy. Molecules and chemical reactions have varying entropy as well. For example, entropy increases as molecules at a high concentration in one place diffuse and spread out. The second law of thermodynamics says that energy will always be lost as heat in energy transfers or transformations. Microorganisms are highly ordered, requiring constant energy input to be maintained in a state of low entropy.

Chemical Reactions

Chemical reactions occur when two or more atoms bond together to form molecules or when bonded atoms are broken apart. The substances used in a chemical reaction are called the reactants (usually found on the left side of a chemical equation), and the substances produced by the reaction are known as the products (usually found on the right side of a chemical equation). An arrow is typically drawn between the reactants and products to indicate the direction of the chemical reaction; this direction is not always a “one-way street.”

An example of a simple chemical reaction is the breaking down of hydrogen peroxide molecules, each of which consists of two hydrogen atoms bonded to two oxygen atoms (H2O2). The reactant hydrogen peroxide is broken down into water, containing one oxygen atom bound to two hydrogen atoms (H2O), and oxygen, which consists of two bonded oxygen atoms (O2). In the equation below, the reaction includes two hydrogen peroxide molecules and two water molecules. This is an example of a balanced chemical equation, wherein the number of atoms of each element is the same on each side of the equation. According to the law of conservation of matter, the number of atoms before and after a chemical reaction should be equal, such that no atoms are, under normal circumstances, created or destroyed.

2H2O2(hydrogen peroxide)⟶2H2O(water)+O2(oxygen)

Some chemical reactions, such as the one shown above, can proceed in one direction until the reactants are all used up. Equations that describe these reactions contain a unidirectional arrow and are irreversible. Reversible reactions are those that can go in either direction. In reversible reactions, reactants are turned into products, but when the concentration of product rises above a certain threshold (characteristic of the particular reaction), some of these products will be converted back into reactants; at this point, the designations of products and reactants are reversed. The changes in concentration continue until a certain relative balance in concentration between reactants and products occurs—a state called chemical equilibrium. At this point, both the forward and reverse reactions continue to occur, but they do so at the same rate, so the concentrations of reactants and products do not change. These situations of reversible reactions are often denoted by a chemical equation with a double-headed arrow pointing towards both the reactants and products. For example, when carbon dioxide dissolves in water, it can do so as a gas dissolved in water or by reacting with water to produce carbonic acid. In the cells of some microorganisms, the rate of carbonic acid production is accelerated by the enzyme carbonic anhydrase, as indicated in the following equation:

CO2+H2Ocarbonicanhydrase⇌H2CO3⇌H++HCO3−

Biology And Chemistry Working Together

The hydrogen and oxygen atoms within water molecules form polar covalent bonds. There is no overall charge to a water molecule, but there is one ∂+ on each hydrogen atom and two ∂– on the oxygen atom. Each water molecule attracts other water molecules because of the positive and negative charges in the different parts of the molecule. Water also attracts other polar molecules (such as sugars), forming hydrogen bonds. When a substance readily forms hydrogen bonds with water, it can dissolve in water and is referred to as hydrophilic (“water-loving”). Hydrogen bonds are not readily formed with nonpolar substances like oils and fats. These nonpolar compounds are hydrophobic (“water-fearing”) and will orient away from and avoid water. The hydrogen bonds in water allow it to absorb and release heat energy more slowly than many other substances. This means that water moderates temperature changes within organisms and in their environments. As energy input continues, the balance between hydrogen-bond formation and breaking swings toward fewer hydrogen bonds: more bonds are broken than are formed. This process results in the release of individual water molecules at the surface of the liquid (such as a body of water, the leaves of a plant, or the skin of an organism) in a process called evaporation.

Conversely, as molecular motion decreases and temperatures drop, less energy is present to break the hydrogen bonds between water molecules. These bonds remain intact and begin to form a rigid, lattice-like structure (e.g., ice). When frozen, ice is less dense (the molecules are farther apart) than liquid water. This means that ice floats on the surface of a body of water. In lakes, ponds, and oceans, ice will form on the surface of the water, creating an insulating barrier to protect the animal and plant life beneath from freezing in the water. If this did not happen, plants and animals living in water would freeze in a block of ice and could not move freely, making life in cold temperatures difficult or impossible.

Because water is polar, with slight positive and negative charges, ionic compounds and polar molecules can readily dissolve in it. Water is, therefore, what is referred to as a solvent—a substance capable of dissolving another substance. The charged particles will form hydrogen bonds with a surrounding layer of water molecules. This is referred to as a sphere of hydration and serves to keep the ions separated or dispersed in the water. These spheres of hydration are also referred to as hydration shells. The polarity of the water molecule makes it an effective solvent and is important in its many roles in living systems.

he ability of insects to float on and skate across pond water results from the property of cohesion. In cohesion, water molecules are attracted to each other (because of hydrogen bonding), keeping the molecules together at the liquid-air (gas) interface. Cohesion gives rise to surface tension, the capacity of a substance to withstand rupture when placed under tension or stress.

These cohesive forces are also related to water’s property of adhesion, or the attraction between water molecules and other molecules. This is observed when water “climbs” up a straw placed in a glass of water. You will notice that the water appears to be higher on the sides of the straw than in the middle. This is because the water molecules are attracted to the straw and therefore adhere to it. 

Cohesion and adhesion are also factors in bacterial colonies and biofilm formation. Cohesion keeps the colony intact (helps it “stick” to a surface), while adhesion keeps the cells adhered to each other. Cohesive and adhesive forces are important for sustaining life. For example, because of these forces, water in natural surroundings provides the conditions necessary to allow bacterial and archaeal cells to adhere and accumulate on surfaces.

The quantitative approach to microbiology to be highly biophysical. However, what a priori I thought it would be the side effect of a microbiologist, turned out to be an interesting description of microbiology from biophysical and mathematical points of view.

BioPhysics: The Odd Couple

Biology needs to transform from a discipline based on phenomena description to one supported by general rules, standardized metrics and therefore able to make predictions. Victor de Lorenzo is the head of the Laboratory of Environmental Molecular Microbiology at the National Center of Biotechnology, an experimental isle within the Systems Biology Department, dominated by theoretical research groups. His laboratory is a mixture of biologists, engineers and network analysts dealing with the domestication of microorganisms for biotechnological purposes, like the elimination or transformation of pollutants by genetic and metabolic modifications of the soil bacterium Pseudomonas putida. One can feel his chemical background as he points out, with criticism, the “absence” of laws and theories in biology: How biology needs to transform from a discipline based on phenomena description to one supported by general rules, standardized metrics and therefore able to make predictions. This is a thought that completely agree with, as I guess will also agree a majority of scientists from areas like mathematics, chemistry and physics: How tremendously is biology being enriched by their contribution! “Only physics is real science, the others are like collecting stamps”, Víctor jokes, to illustrate his line of thought.

This new point of view in biology is developing fast now, and Víctor is a perfect example. Genetic engineering has moved from what it was back in the 80s to what it is nowadays: a precise methodology for designing genetic tools in a logical way for multiple applications. In fact, it can be argued that this more systematic point of view of environmental microbiology has prevented it from disappearing, since previous approximations gave results difficult to extrapolate to naturally occurring environments. As it happens in clinical biology, where unexpected results appear when translating hypotheses from simplistic laboratory experiments to living organisms, in bioremediation a multitude of variables have to be considered. These variables involve, not only single organisms, but also their interactions with a widely diverse surrounding population in a changing environment, where physical and chemical properties affect and constrain their behavior.

Systems biology emerged from the application of network theory to biological processes and became a new conceptual framework for understanding biology, playing an essential role in describing its complexity, by defining behavior patterns and finding logical connections in biological processes. Even today, when the rate of published scientific results is overwhelming, biology still needs to convert vast amounts of information from particular cases to either integrated or transferable ones. Hand in hand goes synthetic biology, which applies similar strategies to modify and create new functions in life. Víctor pioneered this technological handling of microbiology and proudly recalls the first European workshop organized in Spain in 2005 (Constructing and deconstructing life). However, more than thinking of complexity, he pursues optimization through simplification by a systematic genetic manipulation of microorganisms. In contrast to the paradigmatic goal of synthetic biology, that is the creation of an artificial living cell from scratch, he sounds more pragmatic: “Better if we take advantage of millions of years of evolution to our benefit by modifying and controlling already living organisms”.

Besides the Evolution Theory and the Central Dogma, what else do we have?

He is very enthusiastic with this new concept of biology. “Synthetic biology attracts lots of talent, mainly physicists and engineers, since it is a very creative field, where rules and parameters are still to be defined”. But he observes that languages are still very different and communication is not always easy. Other aspects are also under construction; for example, the perspective of classical biology as a descriptive science sometimes underestimates the work of biologists, considered by theorists as mere data generators. As member of several international research boards, he recognizes the effort that physicists, engineers and all those dedicated to synthetic biology are making in finding and defining metrics useful in biology, as something essential for this transformation if we want to standardize laws, rules and metric units. “Besides the Evolution Theory and the Central Dogma, what else do we have?” Víctor says. That being said, more biologists need to populate this area of knowledge for a more integrative development. However, although he acknowledges the great influence of physics over biology, he is more skeptical with some other contributions of biophysics leading to sophisticated techniques; in particular, those related to imaging. In his opinion, converting the study of biology into a “sequence of images”; high quality images, but still surrounded by arbitrary units and qualitative conclusions difficult to reproduce. This worries him and reinforces his idea of working hard in the direction of standardizing and quantitatively measuring biological events.

Basic knowledge in transversal subjects has to be conveyed in all Science degrees: Experimental handling in biochemistry for physicists and a good basis in mathematics for biologists

Is education in biology envisioning this transformation? From the experience at the Complutense University, biophysics and systems biology have minor roles in biology and biochemistry degrees. Víctor recognizes that there is no trivial solution for that. It remains an open discussion and the best model is not yet defined. Postgraduate courses specialized in these areas, when offered to students with very different backgrounds, have very good results in terms of promotion of creativity. However, from Víctor’s experience, the basic knowledge in transversal subjects has to be conveyed in all Science degrees, i.e. experimental handling in biochemistry for physicists and a good basis in mathematics for biologists. Nevertheless, the systematic approach to biology needs to be promoted even more among biologists. For Víctor de Lorenzo, systems and synthetic biology are the latest revolution in biology, essential to universalize hypothesis, create biological theories and make reliable predictions. This latter, however, is the main handicap so far and where most of the criticisms focus on.

Classification of Microorganisms According to Their Relationship to Environmental Factors

Microorganisms could be classified according to the energy and carbon source. Carbon is the basic building block for cell synthesis. Energy must be obtained from outside the cell to enable synthesis to proceed. If the microorganism uses organic material as a supply for carbon, it is called heterotrophic. Autotrophs require only CO2 to supply their carbon needs. Organisms that rely only on the sun as source of energy are called phototrophs. Chemotrophs extract energy from organic or inorganic oxidation/reduction reactions. Organotrophs use organic material, while lithotrophs oxidize inorganic compounds (Davis, 2010; Davis and Cornwell, 2012).

According to the ability to utilize oxygen as a terminal electron acceptor in oxidation–reduction reactions, microorganisms could be classified as obligate aerobes which are the microorganisms that must have oxygen as the terminal electron acceptor. Obligate anaerobes are microorganisms that cannot survive in the presence of oxygen; they cannot use oxygen as a terminal electron acceptor. Facultative aerobes are able to grow with or without oxygen being present. Under anoxic conditions (depleted dissolved oxygen), facultative aerobes utilize nitrites (NO2−) and nitrate (NO3−) as the terminal electron acceptor. Nitrate nitrogen is converted to nitrogen gas in the absence of oxygen. This process is called anoxic denitrification (Davis, 2010; Davis and Cornwell, 2012; Mara and Horan, 2003).

According to the preferred temperature regime, four temperature ranges are used to classify microorganisms. Those that best grow at temperatures below 20°C are called psychrophiles. Mesophiles grow best at temperatures between 25°C and 40°C. Between 45°C and 60°C, the thermophiles grow best. Above 60°C stenothermophiles grow best. The growth range of facultative thermophiles extends from the Microbial Metabolism

Metabolism is the term used to describe all the biochemical reactions that take place inside a cell; it includes those reactions that release energy into the cell, and those that make use of that energy. 

Most microorganisms obtain their energy from the nutrients they take into the cell. These microorganisms break the nutrients into smaller molecules, and then use these molecules for synthesis of new cellular components. They release the chemical energy stored in the nutrients and use it later to perform other processes.

On the other hand, some microorganisms obtain the energy needed for metabolism from the sun by means of photosynthesis (Davis and Cornwell, 2012; Hogg, 2005; Madigan et al., 2014; Tortora et al., 2010; Willey et al., 2016).

Catabolism is the term used to describe reactions that break down large molecules forming smaller molecules, usually associated with a release of energy. Anabolism is the term used to describe reactions involved in biosynthesis of macromolecules, usually requiring an input of energy (Davis and Cornwell, 2012; Hogg, 2005; Madigan et al., 2014; Tortora et al., 2010; Willey et al., 2016).

The energy released in cabalism is used by the microorganisms in different aspects. (Hogg, 2005; Madigan et al., 2014; Tortora et al., 2010; Willey et al., 2016)

The process of metabolism involves the use of some important molecules such as enzymes, and electron and proton carriers.

Biosynthesis and metabolic processes in the cell are generally catalyzed by molecules that are called enzymes which are large molecules usually protein, specific to a particular reaction or group of reactions. Enzymes increase the rate of the reaction by lowering its activation energy through providing alternative pathway for the reaction. Enzymes bring substrates together at spatial places on their surface called active sites. Therefore, chances of effective interaction between substrates are enhanced and the rate increases (Tortora et al., 2010; Willey et al., 2016).

Coenzymes may assist the enzyme by accepting atoms removed from the substrate or by donating atoms required by the substrate. Some coenzymes act as electron carriers, removing electrons from the substrate and donating them to other molecules in subsequent reactions. Many coenzymes are derived from vitamins. Two important coenzymes are encountered while discussing metabolism are nicotinamide adenine dinucleotide (NAD + ) and nicotinamide adenine dinucleotide phosphate (NADP + ); both are derivatives of the B vitamin niacin, and each can exist in an oxidized and a reduced form.

NAD++H++2e−⇌N−ADH

NADP++H++2e−⇌NADPH

NAD+ is primarily involved in catabolic reactions, while NADP+ is primarily involved in anabolic reactions. The flavin coenzymes, such as flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), contain derivatives of the B vitamin riboflavin and are also electron carriers. Cytochromes are another type of electron carriers. Cytochromes are proteins with an iron-containing group that could exist as Fe2 + or Fe3 + (Hogg, 2005; Madigan et al., 2014; Tortora et al., 2010; Willey et al., 2016).

Energy taken up by the cell, either in the form of nutrients or sunlight, must be converted into a usable form. The most usable form of energy is a compound called adenosine triphosphate (ATP). ATP is by far the most important of a class of compounds known as high-energy transfer. ATP stores energy derived from catabolic reactions (such as breaking down of glucose) and releases it later to drive anabolic processes (such as synthetic reactions) and perform other cellular works. ATP molecule (Fig. 10 ) consists of an adenine, a ribose, and three phosphate groups. The terminal phosphate group requires a lot of energy for its formation and is often referred to as a high-energy phosphate bond. When this bond is broken, the same large amount of energy is released, so when ATP is broken down, adenosine diphosphate (ADP) is formed, and energy is released to drive anabolic reactions. hermophilic range into the mesophilic range (Davis, 2010; Davis and Cornwell, 2012).

Cellular Respiration

The term cellular respiration refers to the biochemical pathway by which cells release energy from the chemical bonds of food molecules and provide that energy for the essential processes of life. All living cells must carry out cellular respiration. Respiration could be aerobic or anaerobic according to the availability of oxygen. Prokaryotic cells carry out cellular respiration within the cytoplasm or on the inner surfaces of the cells. In eukaryotic cells the mitochondria are the site of most of the reactions. The energy currency of these cells is ATP, and one way to view the outcome of cellular respiration is as a production process for ATP.

Prokaryotes take the carbohydrates into their cytoplasm, and through a complex series of metabolic processes, they break down the carbohydrate and release the energy. The energy is generally not needed immediately, so it is used to combine ADP with phosphate ions to form ATP molecules. During the process of cellular respiration, carbon dioxide is given off as a waste product. This carbon dioxide can be used by photosynthesizing cells to form new carbohydrates. Also in the process of cellular respiration, oxygen gas is required to serve as an acceptor of electrons. This oxygen gas is identical to the oxygen gas given off in photosynthesis (Hogg, 2005; Madigan et al., 2014; Tortora et al., 2010; Willey et al., 2016).

Glycolysis, in which glucose is oxidized to two molecules of pyruvate with the synthesis of two molecules of ATP. After glycolysis, two options are present depending on the amount of available oxygen. In the presence of oxygen, the cell will undergo aerobic respiration. Without a supply of oxygen, as in an anaerobic environment, the cell will undergo fermentation (Hogg, 2005; Madigan et al., 2014; Tortora et al., 2010; Willey et al., 2016).

Krebs cycle, citric acid cycle (CAC), or the tricarboxylic acid (TCA) cycle: which results in formation of (per two molecules of pyruvic acid) two ATP molecules, six NADH molecules, and two FADH 2 molecules and six CO2 molecules. The NADH and the FADH2 will be used in the electron transport system (Hogg, 2005; Madigan et al., 2014; Tortora et al., 2010; Willey et al., 2016).

Electron transport: In this step NADH and FADH produced in both glycolysis and the Krebs cycle are now being used. Electron transfer takes place in mitochondria in eukaryotic cells. The process is the same in prokaryotes, but it just happens at the main cell membrane. Cytochromes and coenzymes act as carrier molecules and transfer molecules. They accept high-energy electrons and pass the electrons to the next molecule in the system. At key proton-pumping sites, the energy of the electrons transport protons across the cell membrane to the outside (Hogg, 2005; Madigan et al., 2014; Tortora et al., 2010; Willey et al., 2016).

Chemiosmosis, in which the energy given off by electrons is used to pump protons across a membrane and provide the energy for ATP synthesis.

During cellular respiration (Krebs cycle reactions, the electron transport system, and chemiosmosis), 36 molecules of ATP can be produced for each glucose molecule. Additional two ATP molecules are produced through glycolysis, so the net yield is 38 molecules of ATP. These ATP molecules may then be used in the cell for its needs. However, the ATP molecules cannot be stored for long periods of time, so cellular respiration must constantly continue in order to regenerate the ATP molecules as they are used. Each ATP molecule is capable of releasing 7.3 kcal of energy per mole (Hogg, 2005; Madigan et al., 2014; Tortora et al., 2010; Willey et al., 2016).

When oxygen is not available as final electron acceptor, the process of respiration after glycolysis cannot continue as described above. Therefore, an alternative pathway should be present such as fermentation or anaerobic respiration.

Fermentation is an anaerobic pathway for breaking down glucose in which organic carbon is the terminal electron acceptor, one that is performed by many types of organisms and cells. In fermentation, the only energy extraction pathway is glycolysis, with one or two extra reactions tacked on at the end.

Fermentative organisms use NADH and other cofactors to produce many different reduced metabolic by-products, often including hydrogen gas (H2). These reduced organic compounds are generally small organic acids and alcohols derived from pyruvate, the end product of glycolysis. Examples include ethanol, acetate, lactate, and butyrate. Fermentative organisms are very important industrially and are used to make many different types of food products. The different metabolic end products produced by each specific bacterial species are responsible for the different tastes and properties of each food.

Many microorganisms are facultative anaerobes, meaning they can switch between aerobic respiration and anaerobic pathways (fermentation or anaerobic respiration) depending on the availability of oxygen (Hogg, 2005; Madigan et al., 2014; Tortora et al., 2010; Willey et al., 2016).

In the process of anaerobic respiration, carbohydrate can be metabolized by a process that utilizes oxidative phosphorylation via an electron transport chain, but instead of oxygen serving as the terminal electron acceptor an inorganic molecule such as nitrate or sulfate is used. In addition, other organisms may turn to this form of respiration if oxygen is unavailable (facultative anaerobes).

Anaerobic respiration is not as productive as its aerobic counterpart in terms of ATP production, because electron acceptors such as nitrate or sulfate have less positive redox potentials than oxygen. Anaerobic respiration tends to occur in oxygen-depleted environments such as waterlogged soils. It must be underlined here that anaerobic respiration is not the same as fermentation. The latter process does not involve the components of the electron transport chain and generate much smaller amounts of energy (Hogg, 2005; Madigan et al., 2014; Tortora et al., 2010; Willey et al., 2016).

Carbon fixation reaction is usually referred to as CO2 fixation or Calvin cycle. Calvin cycle is the cycle in which carbon is fixed, reduced, and utilized. It involves enzymatically regulated chemical reaction used by autotrophic microorganisms for CO2 fixation. The cycle produces phosphoglycerate and the glyceraldehyde-3-phosphate molecules which are subsequently used to synthesize all the organic compounds needed by the cell. Each turn of the cycle results in the fixation of one molecule of CO2. Therefore, to synthesize one glucose molecule, the cycle must operate six times (Hogg, 2005; Madigan et al., 2014; Tortora et al., 2010; Willey et al., 2016).

The energy generated in the catabolic pathways will be used by cells to manufacture the cellular components (biosynthesis) such as: nitrogenous substances, including proteins and nucleic acids, carbohydrates, including complex polysaccharides (such as capsules and the peptidoglycan of the cell wall), and Phospholipids which are components of the cytoplasmic membrane.

An autotrophic bacterium that can synthesize all its cellular constituents from CO2 and simple inorganic compounds obviously is said to have great biosynthetic ability. In the same way, a heterotrophic bacterium that uses glucose as the only carbon and energy source, ammonium sulfate as the nitrogen and sulfur source, and a few additional inorganic compounds also has great biosynthetic capability. From these nutritional substances, the microorganisms can manufacture anything they need. Bacteria are particularly adept at converting anything they can get hold of into any other item they need.

Glycolysis and the Krebs cycle produce a number of intermediates that can be used in amino acids synthesis. Amino acids can be converted to proteins or they can be incorporated in the production of nucleotides to form nucleic acids. These intermediates can be used also to form more complex carbohydrates. Acetyl CoA from Glycolysis can be oxidized to form fatty acids. Glucose can be converted into just about anything. Fatty acids and amino acids can be catabolized to feed into glycolysis or the Krebs cycle. These pathways are largely reversible and interconnected. Bacteria are extremely resilient, they just need something to work with, and they can manufacture the rest. For example, if they start with protein, they will break it down to amino acids, convert that into pyruvic acid, and be able to form carbohydrates (Hogg, 2005; Madigan et al., 2014; Tortora et al., 2010; Willey et al., 2016).

The Great Unifying Theories Of Biology

In nature, microorganisms seldom live in the isolated single-species colonies as we see on laboratory plates. They more typically live in communities called biofilms. Biofilms are an assemblage of microbial cells; in this assemblage cells stick to each other and often these cells adhere irreversibly. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance (EPS). Biofilms contain also DNA and proteins that are often informally called slime.

Development of Cell Theory

Cell theory is the foundation of modern biology. The British scientist Robert Hooke discovered cells in 1665 by examining very thin slices of cork through a microscope, although he didn't understand their true structure or function, an outline from Saylor Academy states. During the next 200 years, further observations by the scientists Leeuwenhoek, Schleiden, Schwann and Virchow found that all organisms are made up of cells. These units constitute the building blocks of life and occur through the division of pre-existing cells. Understanding these relationships makes it possible to draw some conclusions about the nature of life, including how living things grow and reproduce.

Theory of Evolution

Evolution is considered the single greatest unifying theory in biology, since it offers a comprehensive explanation for the pattern of similarities and differences that exist in all living things, University of Wisconsin-Milwaukee biology professor Andrew J. Petto asserts in an October 2008 position statement for the National Center for Science Education. British naturalist Charles Darwin laid out how evolutionary change occurs in his 1859 book, "The Origin of Species." His core theory is the principle of natural selection, which holds that organisms that adapt to their environment are more likely to survive and leave more offspring, according to the University of Michigan.

Efforts to Unify Biology

Biology didn't become a unified science until the mid-1950s. One factor, University of Florida history of science professor Vassiliki Betty Smocovitis asserts, followed the American Biological Society's formation during that era -- providing one entity to represent its various life sciences. The society's creation coincided with the acceptance of evolution as biology's central unifying theory -- led by thinkers like Julian Huxley, who saw it as verifiable by experimentation and observations. As Smocovitis notes, this situation represented a major shift from the 1930s and 1940s, when academic institutions and publications favored experimental sciences above natural history or descriptive sciences for attention and funding.

Significant Impacts

The influence of cell and evolutionary theories on modern biology becomes clearer after seeing how scientific thinking changed because of them. Cell theory replaced the idea of spontaneous generation, and provided a solidly provable explanation of life processes, such as growth and reproduction. Similarly, Darwin's theory represented a dramatic break from the thinking of his early 19th century colleagues who saw evolution as the outcome of an omnipotent authority's grand design, the University of Michigan's outline states.

Also Search : Two Great Unifying Theories of Biology (seattlepi.com)

Microbiology Career Related Question Answers Found

Is biology easier than chemistry?

A lot of people say that biology is “a lot of memorization” and that chemistry is easier than biology to major in, but these people generally have not taken higher-level biology classes. You really should not choose a major based on which one is “easier” or “harder,” however.

Should I study chemistry or biology?

A lot of people say that biology is “a lot of memorization” and that chemistry is easier than biology to major in, but these people generally have not taken higher-level biology classes. So you should take some time to learn about these more specialized majors too. 

Should I take biology or chemistry?

Whatever introductory biology class you decide to take, you should take chemistry now, including lab, in your first year. You can take introductory biology at the same time, although most students wait until their second year.  

Should I take chemistry or physics?

The traditional approach is to take chemistry first and then physics. In high school I took chemistry my junior year and physics my senior. But after seeing how knowledge of physics makes understanding the reasons why chemical reactions occur the way that they do, I would strongly recommend taking physics first.

How many branches of chemistry are there?

Five

Does biology involve chemistry?

Chemical biology is one field that exists in the overlap between biology and chemistry. They study the chemical reactions that happen inside organisms and the molecular make up of compounds found in organisms. Chemical biology on the other hand involves stimulating biological systems using chemicals.

Which is more important chemistry or physics?

So physics is the most important. Biology and chemistry have done far more to improve the quality of life for people than physics has ever done, chemistry has probably been responsible for the greatest loss of life of all 3 sciences, so biology wins by default.

Is Microbiologist a doctor?

A Doctor, who has done a medical degree, specialises in the field of microbiology, and treats patients with infections. There are also Microbiologists who work in this laboratory, both doctors and non-doctors, who help oversee the work, and interpret results.

Is microbiology a good career?

Yes, it is a good career option. But there will be no shortcut for you as you have to invest about 10–12 years if you would like to be successful in this field. BSc Microbiology is basically study of the micro-organisms which affect human, animal and plant health.

How difficult is microbiology?

Microbiology is a challenging course, to say the least, but a good study strategy can help you to be successful in this course. Read the appropriate sections in your textbook or lab manual before class. Don't simply skim the material, but take the time to try to understand each diagram or figure.

What can we do after BSC microbiology?

Job Profiles:

· Research Assistant.

· Food, Industrial or Environmental Microbiologists.

· Quality Assurance Technologists.

· Sales or Technical Representative.

· Clinical and Veterinary Microbiologists.

· Medical Technologists.

· Biomedical Scientist.

· Clinical Research Associate.

Is there a lot of maths in microbiology?

Yes, a lot.

For any stream of biology, you need to have a basic knowledge of mathematics. In microbiology stream, you have to prepare media and chemicals with appropriate concentration, which requires basic mathematics. When you learn biostatistics, you require a lot of maths.

Where can someone who study microbiology work?

Microbiologists work in hospitals, universities, medical schools, government laboratories, and almost every industry, specializing in a variety of areas, from agriculture to the space industry. 

What does a microbiologist do in a hospital?

In a hospital, their focus is on organisms that cause human disease. Although many microbiologists spend their days in a research lab, a hospital microbiologist is more likely to prepare cultures from specimens, identify and classify various organisms and confirm medical diagnoses through laboratory testing. 

Is Medical Microbiology the same as microbiology?

Hello, general microbiology refers to the general study of microscopic organisms and medical microbiology is science concerned with the prevention , diagnosis and treatment to infectious diseases.