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Microbiology Chapter 7: Elements of Microbial Nutrition, Ecology, and Growth

by: Katelyn Farris

Microbiology Chapter 7: Elements of Microbial Nutrition, Ecology, and Growth BIO 2600

Marketplace > William Carey University > Biology > BIO 2600 > Microbiology Chapter 7 Elements of Microbial Nutrition Ecology and Growth
Katelyn Farris

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These notes cover in depth the elements of microbial nutrition, ecology, and growth. This includes: -Microbial nutrition and essential nutrients -Sources of essential nutrients -Growth factors ...
Dr. Cunningham
Class Notes
Biology, Microbiology, Ecology, Science
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This 5 page Class Notes was uploaded by Katelyn Farris on Monday September 19, 2016. The Class Notes belongs to BIO 2600 at William Carey University taught by Dr. Cunningham in Fall 2015. Since its upload, it has received 4 views. For similar materials see Microbiology in Biology at William Carey University.


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Date Created: 09/19/16
Chapter 7 notes Microbial Nutrition -Nutrition – process by which chemical substances (nutrients) are acquired from the environment and used in cellular activities -Essential nutrients – must be provided to an organism -Two categories of essential nutrients: -Macronutrients – required in large quantities; play principal roles in cell structure and metabolism -Proteins, carbohydrates -Micronutrients or trace elements – required in small amounts; involved in enzyme function and maintenance of protein structure -Manganese, zinc, nickel Nutrients -Organic nutrients – contain carbon and hydrogen atoms and are usually the products of living things -Methane, carbohydrates, lipids, proteins, and nucleic acids -Inorganic nutrients – atom or molecule that contains a combination of atoms other than carbon and hydrogen -Metals and their salts (magnesium sulfate, ferric nitrate, sodium phosphate), gases (oxygen, carbon dioxide) and water Chemical Analysis of Microbial Cytoplasm -70% water -Proteins -96% of cell is composed of 6 elements -Carbon -Hydrogen -Oxygen -Phosphorous -Sulfur -Nitrogen Sources of Essential Nutrients -Carbon sources -Heterotroph – must obtain carbon in an organic form made by other living organisms such as proteins, carbohydrates, lipids, and nucleic acids -Autotroph – an organism that uses carbon dioxide, and inorganic gas as its carbon source -Not nutritionally dependent on other living things Growth Factors: Essential Organic Nutrients -Organic compounds that cannot be synthesized by an organism because they lack the genetic and metabolic mechanisms to synthesize them Chapter 7 notes -Growth factors must be provided as a nutrient -Essential amino acids, vitamins Nutritional Types -Main determinants of nutritional type are: -Carbon source -Heterotroph – uses organic sources of carbon -Autotroph – uses inorganic sources of carbon -Energy source -Chemotroph – gain energy from chemical compounds -Phototrophs – gain energy through photosynthesis Combinations of Nutritional Types -Chemoheterotrophs -Photoautotrophs -Chemoautotrophs (nitrifying bacteria, sulfur bacteria, most of which are members of the Archea) -Photoheterotrophs (purple and green bacteria) Heterotrophs and Their Energy Sources -Two categories -Saprobes: Free-living microorganisms that feed on organic detritus from dead organisms -Parasites: derive nutrients from host -Many pathogens can alternate between these two approaches: opportunistic Transport: Movement of Chemicals Across the Cell Membrane -Passive transport – does not require energy; substances exist in a gradient and move from areas of higher concentration toward areas of lower concentration -Diffusion -Osmosis – diffusion of water -Facilitated diffusion – requires a carrier Transport: Movement of Chemicals Across the Cell Membrane -Active transport – requires energy and carrier proteins; gradient independent -Group translocation – transported molecule chemically altered -Bulk transport – endocytosis, exocytosis, and pinocytosis Environmental Factors That Influence Microbes -Factors include: -Temperature -Oxygen requirements -pH Chapter 7 notes -Osmotic pressure -Barometric pressure -Environmental factors usually affect the function of metabolic enzymes Effects of Temperature on Microbial Growth -Minimum temperature – lowest temperature that permits a microbe’s growth and metabolism -Maximum temperature – highest temperature that permits a microbe’s growth and metabolism -Optimum temperature – promotes the fastest rate of growth and metabolism 3 Temperature Adaptation Groups 1. Psychrophiles – optimum temperature below 15 degrees Celsius; capable of growth at 0 degrees Celsius 2. Mesophiles – optimum temperature 20-40 degrees Celsius; most human pathogens 3. Thermophiles – optimum temperature greater than 45 degrees Celsius Gas Requirements Oxygen -As oxygen is utilized it is transformed into several toxic products: -Singlet oxygen ( O2), superoxide ion (O2), peroxide (H2O2), and hydroxyl radicals(OH) -Most cells have developed enzymes that neutralize these chemicals: -Superoxide dismutase, catalase -If a microbe is not capable of dealing with toxic oxygen, it is forced to live in oxygen free habitats Categories of Oxygen Requirements -Aerobe – utilizes oxygen and can detoxify it -Obligate aerobe – cannot grow without oxygen -Facultative anaerobe – utilizes oxygen but can also grow in its absence -Microaerophilic – requires only a small amount of oxygen Categories of Oxygen Requirements -Anaerobe – does not utilize oxygen -Obligate anaerobe – lacks the enzymes to detoxify oxygen so cannot survive in an oxygen environment Chapter 7 notes -Aerotolerant anaerobes – do not utilize oxygen but can survive and grow in its presence Carbon Dioxide Requirement -All microbes require some carbon dioxide in their metabolism -Capnophile – grows best at higher CO t2nsions than normally present in the atmosphere Effects of pH -Majority of microorganisms grow at a pH between 6 and 8 -Obligate acidophiles – grow at extreme acid pH -Alkalinophiles – grow at extreme alkaline pH Osmotic Pressure -Most microbes exist under hypotonic or isotonic conditions -Halophiles – require a high concentration of salt -Osmotolerant – do not require high concentration of solute but can tolerate it when it occurs Other Environmental Factors Barophiles – can survive under extreme pressure and will rupture if exposed to normal atmospheric pressure Ecological Associations Among Microorganisms -Symbiotic – two organisms live together in a close partnership -Mutualism – obligatory, dependent; both members benefit -Commensalism – commensal member benefits, other member neither harmed nor benefited -Parasitism – parasite is dependent and benefits; host is harmed -Non-symbiotic – organisms are free-living; relationships not required for survival -Synergism – members cooperate to produce a result that none of them could do alone -Antagonism – actions of one organism affect the success or survival of others in the same community (competition) -Antibiosis Interrelationships Between Microbes and Humans -Human body is a rich habitat for symbiotic bacteria, fungi, and a few protozoa – normal microbial flora -Commensal, parasitic, and synergistic relationships Microbial Biofilms -Biofilms result when organisms attach to a substrate by some form of extracellular matrix that binds them together in complex organized layers Chapter 7 notes -Dominate the structure of most natural environments on earth -Communicate and cooperate in the formation and function of biofilms – quorum sensing The Study of Microbial Growth -Microbial growth occurs at two levels: growth at a cellular level with increases in size, and increase in population -Division of bacterial cells occur mainly through binary fission (transverse) -Parent cell enlarges, duplicates its chromosome, and forms a central transverse septum dividing the cell into two daughter cells Rate of Population Growth -Time required for a complete fission cycle is called the generation, or doubling time -Each new fission cycle increases the population by a factor of 2 – exponential growth -Generation times vary from minutes to days The Population Growth Curve -In laboratory studies, populations typically display a predictable pattern over time – growth curve -Stages in the normal growth curve: 1. Lag phase – “flat” period of adjustment, enlargement; little growth 2. Exponential growth phase – a period of maximum growth will continue as long as cells have adequate nutrients and a favorable environment 3. Stationary phase – rate of cell growth equals rate of cell death caused by depleted nutrients and O 2 ,xcretion of organic acids and pollutants 4. Death phase – as limiting factors intensify, cells die exponentially


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