Metabolism
The set of chemical reactions is controlled. These cells—are a key characteristic of all living things. The result of metabolic activity is reproduction. The increase in the number of individual cells or organisms. When referring to the general reproductive functions of microorganisms and bacteria.
In particular, Microbiologists use growth. To mean an increase in the number of microbes. Rather than an increase in the size of an individual. The result of such microbial growth is either an isolated colony formed. From only one progenitor cell or a biofilm.
Put another way, the reproduction of individual microorganisms results. In the growth of a colony or biofilm. Too, common expressions such as "microorganisms grew. In media containing salt" are understood to mean that the organisms grow in size. Metabolism and reproduction instead.
In this chapter, we approach the characteristics of microbial evolution from two different. But related perspectives we microbiologists examine. The needs of microorganisms living in their natural environment. Including their chemical, physical, and energetic requirements.
And we also find out that microbiologists try to create similar conditions. To grow microorganisms in the laboratory. So that they can be transported, identified, and studied. Let us conclude by examining some techniques for measuring population growth.
Growth Requirements
Organisms use a variety of chemo-nutrients to meet their energy needs. And to build biological molecules and cellular structures. The most common of these nutrients are compounds. They contain essential elements such as carbon, oxygen, nitrogen, and hydrogen.
Like all organisms, microorganisms get nutrients. From various sources in their environment. And must transport their nutrients into their cells. By passive and active transport processes.
Nutrients Chemical and Energy Requirements
We study the three things necessary for our microbial growth needs. That all cells need for metabolism. A carbon source, a source of energy. And a source of electrons or hydrogen atoms.
Sources of Carbon, Energy, and Electrons
Organisms can be classified into two broad groups based on their source of carbon. Organisms that use carbon dioxide as the sole. The source of their carbon is called autotrophs hence the name "own themselves". "eating". More microscopic, autotrophic make organic compounds from CO.
And thus do not need to get carbon from other organisms. In contrast, organisms are called heterotrophs. Catabolism reduces biological molecules.
Organisms can be classified in such a way that they use chemicals or light as a source of energy.
Organisms that get energy from redox reactions involving. Inorganic and organic chemicals are called chemotrophs. These reactions are either aerobic respiration or anaerobic respiration. Or fermentation depending on the final electron acceptor.
Thus, we see that organisms can be classified into four basic groups. Based on their carbon and energy sources photoautotrophs, chemoautotrophs, photoheterotrophs, and chemoheterotrophs. Plants, some protozoa, and algae are photoautotrophs.
And animals, fungi, and other protozoa are chemoheterotrophs. Bacteria and Puraceae exhibit greater metabolic diversity. Than any other group, including members of all four groups.
Additionally, the cells of all organisms. Need electrons or hydrogen atoms for redox reactions. Hydrogen is the most common chemical element in cells. And it is so common in organic molecules and water. That it is never the limiting nutrient.
There is never a shortage of hydrogen. Hydrogen is essential in hydrogen bonding and electron transfer.
Heterotrophs get electrons from the same organic molecules. That provides them with carbon and is called organography. Autotrophic organisms get electrons from inorganic molecules. Or get hydrogen molecules and are called lithotrophs.
Oxygen Requirements
The bind aerobes must be oxygen because it acts. As the final electron acceptor of the electron transport chain. Which produces most of the ATP in these organisms. In contrast, oxygen is a lethal toxin for binding aerobes. How can oxygen be essential for one group of people? And yet be a deadly poison for others.
The key to understanding this clear inconsistency. Is that neither atmospheric oxygen (O) nor bound oxygen? Such as carbohydrates and water are toxic. Rather, toxic forms of oxygen are those that are reactive. These are toxic.
This is the reason why oxygen is the final electron acceptor of aerobes. They are excellent oxidizing agents so they steal electrons from other compounds. The resulting powerful oxidation chain causes irreparable damage to cells. By oxidizing important compounds, including proteins and lipids.
There are four toxic forms of oxygen
Singlet oxygen is a molecular oxygen with electrons raised. To a higher energy state during aerobic metabolism singlet oxygen.
Gen is a very reactive oxidizing agent. Phagocytic such as some human white blood cells. It is used to oxidize pathogens. Since singlet is a photochemical produced. By the reaction of oxygen and light, phototrophic microorganisms. Often contain pigments called carotenoids that reduce toxicity.
Superoxide radicals (0,). Some peroxide radicals are formed. In the presence of oxygen during the incomplete reduction. During electron transport in aerobics, and metabolism by anaerobes. Superoxide radicals are so reactive and toxic. That aerobic organisms must be able to detoxify them.
For this, an enzyme called superoxide dismutase (DMU-data) must be produced. These enzymes contain metal 2, MENTON2, FI2T, F2 + NI2 + or CU2. These enzymes break down hydrogen peroxide (HO) and molecular oxygen (HO). Two superoxide radicals and two protons combine to form.
2O2 +2H→H2O2 + O2
One of the reasons that anaerobes are considered sensitive to oxygen is. Is that they do not undergo superoxide dismutase. They are destroyed as a result of oxidation. Reactions of superoxide radicals are produced in the presence of oxygen.
The peroxide anion (0,2)hydrogen peroxide is formed during reactions catalyzed. By superoxide dismutase containing the peroxide anion, another reactive oxidant. The peroxide anion is what makes hydrogen peroxide an antimicrobial agent. Aerobes contain either catalase or peroxidase, enzymes that detoxify peroxide ions.
2H2O2 → 2H2O + O 2
The production of bubbles of oxygen indicates the presence of catalase. Peroxidase breaks down hydrogen peroxide without an oxygen coenzyme node.
H2O2 + NADH + H + + → 2 H2 O + NAD +
Bind anaerobes either lack both catalase and peroxidase. So they are susceptible to the toxic action of hydrogen peroxide.
Ionizing radiation and incomplete reduction of hydrogen peroxide result. The formation of hydroxyl radicals (OH-)hydroxyl radicals.
H2O2+ e + H → H2O + OH
Hydroxyl radicals are the most reactive of the four toxic forms of oxygen. Because hydrogen peroxide does not accumulate in aerobic cells. The danger of hydroxyl radicals is eliminated in aerobic cells.
Also the enzymes superoxide scavengers. Catalase and peroxidases, aerobes use other antioxidants. Such as vitamins C and E to protect themselves from toxic oxygen products. Many organisms can live in different oxygen concentrations between these two extremes.
For example, some aerobic organisms can sustain life by fermentation or atmospheric respiration. Although their metabolic efficiency is often reduced. In the absence of oxygen. Such organisms are called commensal organisms
Escherichia coli is an example of a facultative anaerobic bacterium. Aerobic anaerobes do not use aerobic metabolism but they do tolerate oxygen. The lactobacilli that turn cucumbers into pickles and milk into cheese are anaerobic.
Microaerophiles such as the ulcer-causing pathogen. Helicobacter pylori must have oxygen levels of 2% to 10%. 21% of the oxygen in the atmosphere Microaerophiles are damaged. By high CO concentrations, because they have limited ability. To detoxify hydrogen peroxide and superoxide radicals.
Microbial groups contain members of each of the five types of oxygen rule. Some yeasts and many prokaryotes are facultative anaerobes. Many prokaryotes and some protozoa are aerobic, microaerophilic, or bind anaerobes. The oxygen rule of an organism can be identified. By growing it in a medium that has an oxygen gradient from top to bottom.
Nitrogen Requirements
Another essential element is nitrogen. Which is contained as part of many organic compounds. Amino acids, and nucleotide bases. Nitrogen accounts for about 14% of the dry weight of microbial cells. Nitrogen is often the growth-limiting nutrient for many organisms.
Their anabolism ceases because they do not have enough nitrogen. To make proteins and nucleases. Organisms get nitrogen from organic and inorganic nutrients.
For example, most photosynthetic organisms can reduce nitrate. To ammonium which can then be used for biosynthesis. Too, all cells recycle nitrogen from their amino acids and nucleotides.
Although nitrogen accounts for about 79% of the atmosphere. Few organisms can use nitrogen gas. Some bacteria, especially cyanobacteria and rhizobium. Can reduce nitrogen gas to ammonia through a process called nitrogen fixation.
Nitrogen fixation is essential for life on Earth because nitrogen fixers provide nitrogen. In a usable form to other organisms. Carbon, hydrogen, oxygen, and nitrogen together make up more than 95% of the dry weight of cells. Other chemical requirements. Phosphorus, sulfur, calcium, manganese, magnesium, copper, and iron. And some other trace elements are the rest.
It is a component of sulfur-containing amino acids. Which are linked to each other and form proteins. They are important for the tertiary structure of calcium and contain vitamins. Such as thiamine and biotin.
Other elements are called trace elements. Because they are needed in very small amounts. For example, the few atoms of selenium depleted. The walls of a glass tube are needed for the growth of green algae in the laboratory.
Other trace elements These are usually found in enough quantities. To dissolve in water. For this reason, tunnel water is sometimes used. In place of distilled or deionized water for the production of microorganisms. In the laboratory.
Some microorganisms—for example, algae and photosynthetic bacteria—are lithotrophic photoautotrophs. They can synthesize their metabolic and structural needs from inorganic nutrients. They contain all the enzymes. And cofactors needed to produce all their cellular components.
But, most organisms must certain organic chemicals, which they cannot synthesize. With carbon and energy-providing chemical substances. These essential organic chemicals are called growth factors.
For example, some Vitamins are Roth factors for microorganisms. Remember that vitamins are parts of many or many coenzymes. Different microbes have Growth factors. Including certain amino acids, purines, pyrimidines, cholesterol, NADH, and heme.
Physical Requirements
Also to chemical nutrients, organisms have physical growth requirements. That includes specific conditions of temperature, pH, osmolarity, and pressure.
Temperature
Temperature plays an important role in microbial life through. The three-dimensional configuration of biological molecules. To function, proteins need a three-dimensional shape. That is determined by temperature-sensitive hydrogen bonds. Degradation is more likely to occur at lower temperatures.
And it is also more likely to break high temperatures. When hydrogen bonds are broken, proteins are disrupted and function is lost. Also, components of the membranes of cells and organelles. Such as lipids, are temperature sensitive.
If the temperature is too low, the membrane becomes rigid and fragile. If the temperature is too high, the number of lipids becomes more fluid. And the cell or organelle elements are no longer in the membrane.
Because temperature plays an important role. In the tetragonal structure of many types of biological molecules. Different temperatures have different effects on the survival and growth of microbes. The lowest temperature at which an organism can conduct metabolism. Is called the smallest brown temperature.
But, many microbes, especially bacteria, survive well below this temperature. Even though cell membranes are less fluid and transport processes. Metabolism is too slow to support activity. The highest temperature at which an organism continues to metabolize. Is called the largest growth temperature.
When the temperature rises above this value. The proteins of the organism become denatured. are, and it dies. Activities producing the highest growth rates are the most types of temperatures.
Thus every organism survives. At temperature range within which its growth and metabolism are supported. Based on their preferred temperature range—where their metabolic activity. And growth is best supported—microbes can be classified into four overlapping groups.
It grows best at temperatures below 0 °C and continues to grow. Temperatures below 0 °C. They die. Temperatures above 20 °C. In nature, necrophilic algae, fungi, archaea, and bacteria live. In areas of snow, ice and cold water live.
They do not cause disease in humans because they cannot grow at body temperature. Some cause food wastage in refrigerators. Psychrophiles pose unique challenges for laboratory investigation because they must be kept cold.
For example, under microscope conditions must be refrigerated. And the air temperature required to maintain the psychrometer. Is cold for the lab staff.
Are organisms that grow best in temperatures ranging from 20 °C to 40 °C, although. They can survive at higher and lower temperatures. Because the body temperature is around 37 °C, human pathogens.
Mesophiles are thermophilic organisms that can survive for brief periods at high temperatures. Thermionic mesophiles can destroy food due to insufficient heating during pasteurization and canning.
Thermophiles? Compost heaps and hot springs. Some members of Puraceae are called hyperthermophiles. Thrive in water above 80 °C. Others live. At temperatures above 100 °C. The current record-holder archetype is Bhuagemma bars.
Bhughemma grows and breeds near submarine hot springs. At temperatures between 85 °C and 121, °C can survive. At least two hours at 130 °C. Thermophiles and hyperthermophiles stabilize their proteins. With extra hydrogen and covalent bonds between amino acids.
Heat-loving organisms do not cause disease because they are not present in the body. Beneficial microbes A nuclear waste-eating microbe? 206 in P highlights exceptional thermophiles that can withstand radiation.
pH
Organisms are sensitive to changes in acidity because of hydrogen ions. And hydroxyl ions disrupt hydrogen bonding within proteins. And nucleic acids as a result. Organisms have a range of acidity that they prefer and can tolerate.
pH A measure of the concentration of hydrogen ions in a solution. It is a measure of the acidity or alkalinity of a substance. A pH below 7.0 is acidic; the lower the pH value. The more acidic a substance is. The alkaline pH value is greater than 7.0.
Most bacteria and protozoa, including most microbes, grow best. In a narrow range around neutral pH—that is, between p6.5 and p7.5. Which is the pH level of most tissues and organs in the human body.
Such microbes are also called neutrophils. Other bacteria and many fungi are acidophiles. In contrast, acidophiles and many fungi are organisms that live in acidic habitats.
An example of acidophilic microbes is the chemotrophic prokaryotes. They live in mines and mines. Live in water that goes through tailings their habitats have fractions below 0.0. These prokaryotes oxidize.
Sulfur leads to the pH of sulfuric acid and the pH. But, bind acidophiles must an acidic environment. And if the pH drops to 7.0, acid-resistant microbes can only survive in acid but do not like it.
Many organisms produce acidic waste products. They accumulate in their environment until they stop growing. For example, many kinds of cheese are acidic due to lactic acid caused by bacteria and fungi.
This type of cheese has a low pH and further microbial growth can be prevented. Pickling other acidic foods such as sauerkraut. And dill prevents spoilage because most organisms cannot tolerate its pH.
The normal acidity of different areas of the body inhibits microbial growth. And protects against a variety of infections. The acidity produced by the vagina of adult women. One site results from the fermentation of carbohydrates. By normal resident bacteria.
If the Growth of normal inhabitants is inhibited. For example, antibiotic therapy—results in high pH. That can lead to waste growth and yeast infections. Another abdominal site is inhospitable to most microbes.
Due to the normal production of stomach acid. Yet, the acid-resistant bacterium. Helicobacter pylori neutralize stomach acid. By secreting bicarbonate and urea, which converts urea into ammonia, which is alkaline. The growth of Helicobacter is due to alkaline conditions.
That most microbes prefer. Inhibits the growth of P. but alkaline soils keep alkaline soils and water up to pH 11.5. For example, Vibrio cholera, which causes cholera, can increase the pH outside the body. Breeds on 9.0.
Physical Effects of Water
Microorganisms must water; they must be kept. In a moist environment if they are to be active. Water is needed to dissolve enzymes and nutrients. Also, it plays an important role in many metabolic reactions. Although most cells die in the absence of water.
Some microorganisms-mycobacterium cell walls. That keeps water and allows them to survive for months in dry conditions. Also, have spores and cysts of some other unicellular bacteria. Give up metabolic activity in a dry environment for years.
These cells are actually in a state of living as they neither grow nor die in their dry state. does reproduction. We now turn to the physical effects of water on microorganisms. By examining two topics—osmotic pressure and hydrostatic pressure.
Osmotic pressure is the diffusion of water across a membrane. And is induced by unequal solvent concentrations on both sides of such a membrane. The osmotic pressure of a solution is the pressure exerted on a membrane.
By solution containing solutes that exist in free form. Cannot cross the membrane. Osmotic pressure is related to the concentration of dissolved molecules. And ions in the solution.
Solutions with a higher concentration of such solute solvents. Are those with a lower solute concentration, hypotonic? Osmotic pressure can affect cells. For example, a cell placed in freshwater relative.
Receives water from its environment and expands to the extent of its cell wall. Cells that lack cell membranes and some bacterial, and fungal. And protozoan cells swell unless They will not swell in hypotonic salves.
A cell placed in seawater contains a solution of about 3.5% solvents. And is thus hypertonic to most cells, and loses water to the surrounding water from salts. Such a cell may die from embolism or its cytoplasm spiciness.
Osmotic pressure is the cause of the salt shake. And the preserving action of the sugars in salted fish and jellies. The sugars and salt in these foods act as solvents. Drawing water out of the microbial cells present. And prevent their growth and reproduction.
Osmotic pressure restricts organisms to certain environments. Some microbes are called facultative halophiles. Are adapted to growth by high osmotic pressure. They can grow up to 30% salt and explode when exposed to fresh water. Other microbes have been called experimental halophiles. And yes, there is no need for high amounts of salt, but they can tolerate it.
It can tolerate up to 20% salt, which allows it to colonize. The surface of the skin—and the environment are too salty for most microbes. Aureus causes a variety of skin. d mucous membrane diseases ranging from pimples, acne, and styles. And boils to life-threatening scaly skin and toxic shock syndrome.
