Microbial Nutrition, Ecology, and Growth PDF

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This lecture was led by Paul Himes and covers the topics of Microbial Nutrition, Ecology, and Growth...

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Microbial Nutrition, Ecology, and Growth Lecture led by Paul Himes

Microbes Must Obtain Nutrients from Environment ● If we want to live/grow, we need: ○ Source of elements ■ For building macromolecules ■ Anabolic reactions ■ Some are essential nutrients ● Substances that must be provided to organism ● Can’t make them ● Need to get from diet ○ Need macronutrients and micronutrients (trace elements) ○ Acquired from reservoir in environment ○ Can be categorized according to C content ■ Inorganic nutrients vs Organic nutrients

Microbial Nutrition Strategies ● Carbon Source: ○ What do we call organisms that make their own organic molecules from CO2? ○ What do we call organisms that get organic carbon from their food? ● Energy Source: ○ What do we call organisms that get energy from sunlight? ○ What do we call organisms that get energy from eating chemicals? ● Every combination is possible and does exist ● Saprobes (Saprophytes) ○ Free living molecules ■ Not pathogens ○ Decomposers - get their C from eating dead things ■ Can degrade: Plant litter, Animal matter, Dead microbes ○ Chemoheterotrophs ○ Most have rigid cell wall (fungi/bacteria) ■ Can’t engulf food ■ Release enzymes → environment → digest food particles → smaller molecules then can be imported via pores in membrane ● Obligate Saprobes → exist strictly on dead organic matter in soil and water ○ Need to be free living, can’t infect host ○ Not as common as once thought ● More and more commonly, what we thought to be obligate saprobes are found to be facultative parasites/opportunistic pathogens

○ Don’t infect everything, but can infect susceptible hosts ■ Things with weakened or damaged immune responses ○ Host not primary habitat ■ Not saprobes first choice ■ If nothing stops it, will treat host like dead stuff to decay ● Parasites ○ Derive nutrients from cells or tissues of host ○ Differ from saprobes in that they get their C from other things that are still alive ○ Chemoheterotrophs ○ Not all parasites damage the host directly ■ May steal the host’s food ○ Pathogens → cause damage to tissues or even death as they take C and energy from host ● Types of parasites (location based) ○ Ectoparasites - live on the body ○ Endoparasites - live in the body (organs and tissues) ○ Intracellular Parasites - live within the cells ○ Obligate Parasites - unable to grow outside of a living host

Macronutrients - Hydrogen ● Major part of all organic and many inorganic compounds ● Performs overlapping roles in the biochemistry of cells: ○ Maintaining pH ○ Forming hydrogen bonds between molecules ○ E- transport during respiration/photosynthesis → H+ gradient → free energy for: ■ ATP synthesis ■ Flagella rotation

Macronutrients - Nitrogen ● Mainly found in: ○ DNA ○ RNA ○ Proteins ● Main reservoir - N2 (the atmosphere) ○ Used in cells as -NH3 ■ Only form that can be attracted to C ■ Primary nitrogen source for heterotrophs

Macronutrients - Oxygen ● Major component of organic compounds ● Also found in inorganic salts ○ Phosphates ○ Sulfates ○ Nitrates ○ H20 ● Terminal electron acceptor in aerobic respiration ○ Strongest oxidizing agent ● O2 makes up 20% of the atmosphere ● Not everything can use atmospheric O2 ○ Or even survive when it’s present

Macronutrients - Phosphorus ● Mainly used as Phosphate (PO43-) ○ Key component in nucleic acids ○ Also found in ATP ○ Regulate protein activity ○ Phospholipids in cell membranes and coenzymes

Macronutrients - Sulfur ● ● ● ● ●

Widely distributed throughout environment in mineral form Essential component of some vitamins (B1) Amino acids - methionine and cysteine Crucial for photosynthesis Coenzyme A ○ Connection between glycolysis and Krebs cycle ○ Part of fatty acid biosynthesis/degradation ● Energy donor for some anaerobes

Other Elements ● ● ● ● ● ●

Potassium (K) - Protein synthesis, membrane function, and help with transport Sodium (Na) - Cell transport, action potential Calcium (Ca) - Stabilizer Magnesium (Mg) - Found in chlorophyll and a cofactor in enzymes Iron (Fe) - Found in cytochrome and hemoglobin Zinc (Zn) - A regulatory element...