Chapter 07

Chapter 07

Microbial Nutrition Nutrition: Nutrients are acquired from the environment and used for cellular activities Essential nutrient: Any substance, whether in elemental or molecular form, that must be provided to an organism Macronutrients: Required in relatively large quantities Play principal roles in cell structure and metabolism Micronutrients (trace elements): Present in smaller amounts Involved in enzyme function and maintenance of protein structure Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 1

Inorganic versus Organic Nutrients Inorganic nutrients: Atom or simple molecule that contains a combination of atoms other than carbon and hydrogen Organic nutrients: Contain carbon and hydrogen atoms Usually the product of living things Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 2 Principal Inorganic Reservoirs of Elements Carbon in air; in rocks and sediments Oxygen in air, certain oxides, water Nitrogen in air; , , in soil

and water HydrogenWater, gas, mineral deposits PhosphorusMineral deposits (, ) SulfurMineral deposits, volcanic sediments (, ) PotassiumMineral deposits, the ocean (, ) SodiumMineral deposits, the ocean (NaCl, NaSi) CalciumMineral deposits, the ocean (, ) MagnesiumMineral deposits, geologic sediments () ChlorideThe ocean (NaCl, ) IronMineral deposits,

geologic sediments () Manganese, molybdenum, cobalt, nickel, zinc, copper, other micronutrients various geologic sediments Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 3 Analysis of the Chemical Composition of an Escherichia coli Cell Organic Compounds Proteins RNA DNA Carbohydrates Lipids Miscellaneous

Inorganic Compounds Water All others % Total Weight 15 6 1 3 2 2 % Total Weight 70 1

% Dry Weight 50 20 3 10 10 4 % Dry Weight 3 Element % Dry Weight Carbon (C) 50

Oxygen (O) 20 Nitrogen (N) 14 Hydrogen (H) 8 Phosphorus (P) 3 Sulfur (S) 1

Potassium (K) 1 Sodium (Na) 1 Calcium (Ca) 0.5 Magnesium (Mg) 0.5 Chlorine (Cl) 0.5

Iron (Fe) 0.2 Trace metals 0.3 Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 4 Carbon Sources: Heterotroph An organism that must obtain its carbon in organic form Dependent on other life forms Most carbon sources exist in a form that is simple enough for absorption Larger molecules must be digested by the cell before

absorption Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 5 Carbon Sources: Autotroph Self-feeder Organism that uses inorganic as its carbon source Have the capacity to convert into carbon compounds Not nutritionally dependent on other living things Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 6 Nitrogen Sources Main reservoir is nitrogen gas (), 79% of atmosphere

indispensable to structure of proteins, DNA, RNA, and ATP Primary nitrogen sources for heterotrophs Must be degraded into basic building blocks in order to be utilized Some bacteria and algae utilize inorganic nitrogenous nutrients (, , or ) Regardless of the source, nitrogen must be converted to before it enters the cell This is the only form that can be directly combined with carbon to synthesize amino acids and other compounds Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 7 Oxygen Sources Oxygen plays an important role in the structural and enzymatic functions of the cell Major component of carbohydrates, lipids, nucleic acids and

proteins Common component of inorganic salts makes up 20% of atmosphere Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 8 Hydrogen Sources Overlapping roles in the biochemistry of cells: Maintaining pH Forming hydrogen bonds between molecules Serving as the source of free energy in oxidationreduction reactions of respiration Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 9

Phosphorus (Phosphate) Sources Main inorganic source is phosphate () Derived from phosphoric acid () Found in rocks and oceanic mineral deposits Key component of nucleic acids Essential to genetics of cells and viruses Found in ATP, important energy molecule in cells Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 10 Sulfur Sources Widely distributed throughout the environment in rocks and sediments Essential component of some vitamins (vitamin ) and amino acids methionine and cysteine

Form disulfide bonds that help determine the shape and structural stability of proteins Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 11 Essential Organic Nutrients Growth factor: An organic compound such as an amino acid, nitrogenous base, or vitamin that cannot be synthesized by an organism Example: essential amino acids Must be provided by the environment Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12

Nutritional Categories of Microbes by Energy and Carbon Source Category/Carbon Source Autotroph/ 1. Photoautotroph 1. Photoautotroph Energy Source 2. Chemoautotroph 2. Chemoautotroph Simple inorganic chemicals Simple inorganic chemicals Category/Carbon Source Heterotroph/Organic 1. Photoheterotroph

2a. Chemoheterotroph: Parasite 2b. Chemoheterotroph: Saprobe Energy Source Example Other Organisms or Sunlight Sunlight Utilizing the tissues, fluids of a live host Metabolizing the organic matter of dead organisms Purple and green photosynthetic bacteria Various parasites and pathogens; can be bacteria, fungi, protozoa, animals Fungi, bacteria

Nonliving Nonliving Environment Environment Sunlight Sunlight Example Photosynthetic organisms, such as algae, Photosynthetic organisms, such as algae, plants, cyanobacteria plants, cyanobacteria Only certain bacteria or archaea, such as methanogens, deep-sea vent bacteria Only certain bacteria or archaea,

such as methanogens, deep-sea vent bacteria Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 13 Aerobic Respiration Principal energy-yielding pathway in animals, protozoa, fungi, and aerobic bacteria Complementary to photosynthesis Glucose and oxygen are reactants, and carbon dioxide is given off Earths balance of energy and metabolic gases is dependent on this reaction Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 14

Saprobic Microorganisms Decomposers of plant litter, animal matter, and dead microbes Important in recycling nutrients held in organic materials Most saprobes have a rigid cell wall and cannot engulf large particles of food Bacteria and fungi Release enzymes into the environment to digest food into smaller particles that can be transported into the cell Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 15 How Microbes Feed: Nutrient Absorption Necessary nutrients must be taken into the cell and

waste materials must be transported out of the cell Transport occurs across the cell membrane Structure specialized for transport Cell wall is too nonselective to screen the entrance or exit of molecules Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 16 Diffusion The movement of molecules in a gradient from an area of higher density or concentration to an area of lower density or concentration Diffusion across a cell membrane is determined by the concentration

gradient and the permeability of the substance Jump to long description Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 17 The Movement of Water: Osmosis Osmosis: The movement of water across a selectively permeable membrane The membrane is selectively or differentially permeable: has passageways that allow the passage of water but not other dissolved molecules Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 18 Environmental Factors That Influence Microbes

Heat Cold Gases Acid Radiation Osmotic pressure Hydrostatic pressure Other microbes Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

19 Cardinal Temperatures Cardinal temperatures: range of temperatures for the growth of a given microbial species Minimum temperature Maximum temperature Optimum temperature Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 20 Minimum and Maximum Temperatures Minimum temperature: The lowest temperature that permits a microbes continued growth and metabolism Below this temperature, its activities are limited Maximum temperature:

Highest temperature at which growth and metabolism can proceed If the temperature rises slightly above maximum, growth will stop If the temperature continues to rise, enzymes and nucleic acids will become denatured, or permanently inactivated Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 21 Optimum Temperature Optimum temperature: Intermediate temperature range between minimum and maximum Promotes the fastest rate of growth and metabolism Small chemical differences in bacterial membranes which affect their fluidity allow them to thrive at different temperatures Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

22 Psychrophiles Organisms that have an optimum temperature below 15C Capable of growth at 0C Cannot grow above 20C Psychrotrophs: grow slowly in the cold, but have an optimum temperature between 15C and 30C (a) Francois Gohier/Science Source; (b) Courtesy Nozomu Takeuchi Jump to long description Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 23

Mesophiles Majority of medically significant organisms Individual species can grow from 10C to 50C Optimum growth temperature: 20C to 40C Most human pathogens: 30C to 40C Thermoduric microbes survive short exposure to high temperatures; common contaminants of heated or pasteurized foods Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 24

Thermophiles Grow optimally at temperatures above 45C Live in soil and water associated with volcanic activity, compost piles, habitats directly exposed to the sun General range of growth: 45C to 80C Extreme thermophiles grow between 80C and 121C Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 25 Gases Oxygen has the greatest impact on microbial growth Microbes fall into one of the three categories: Those that use oxygen and can detoxify it Those that can neither use oxygen nor detoxify it Those that do not use oxygen but can detoxify it Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

26 Oxygen Requirements Aerobe (aerobic organism): Can use gaseous oxygen in its metabolism Possesses the enzymes needed to process toxic oxygen products Obligate aerobe: an organism that cannot grow without oxygen Facultative anaerobe: An aerobe that does not require oxygen for its metabolism Capable of growth in the absence of oxygen Metabolizes by aerobic respiration when oxygen is present

Adopts anaerobic metabolism (fermentation) when oxygen is absent Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 27 Oxygen Requirements Microaerophile: Does not grow at normal atmospheric concentrations of oxygen Requires a small amount of oxygen in its metabolism Usually live in a habitat that provides a small amount of oxygen but is not directly exposed to the atmosphere Anaerobe (anaerobic microorganism): Lacks the metabolic enzyme systems for using oxygen in respiration Strict or obligate anaerobes cannot tolerate free oxygen and will die in its presence Live in highly reduced habitats such as lakes, oceans, and soil

Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 28 Culturing Techniques for Anaerobes Jump to long description Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the(a) prior written consent of McGraw-Hill Education. Hank Morgan/Science Source 29 Oxygen Requirements

Aerotolerant anaerobes: Do not utilize oxygen Can survive and grow to a limited extent in its presence Not harmed by oxygen because they possess alternative mechanisms for breaking down peroxides and superoxide Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 30 Carbon Dioxide Requirements Capnophiles: Grow best at a higher tension than is normally present in the atmosphere Important in the isolation of some pathogens Incubation is carried out in a incubator that provides 3 to 10% Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 31

pH pH: the degree of acidity or alkalinity of a solution expressed on a scale from 0 to 14 Pure water is neutral at pH 7.0 As the pH value decreases toward 0, acidity increases As the pH value increases toward 14, alkalinity increases Obligate acidophiles: Require an acidic environment for growth Molds and yeasts tolerate acid and are common spoilage agents of pickled

foods Alkalinophiles: Live in hot pools and soils that contain high levels of basic minerals Bacteria that decompose urine create alkaline conditions Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 32 Symbiosis Symbiosis: a general term used to denote a situation in which two organisms live together in a close partnership

Mutualism: exists when organisms live in an obligatory but mutually beneficial relationship Corbis RF Jump to long description Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 33 Symbiosis Commensalism: relationship benefits one member and not the other Commensal: receives benefits Coinhabitant: neither harmed nor benefitted Parasitism:

Host: provides the parasitic microbe with nutrients and a habitat Parasite: multiplication of the parasite usually harms the host to some extent Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 34 Nonsymbiotic Associations Antagonism: Synergism: Arises when members of a community compete One microbe secretes chemical substances into the surrounding environment that inhibit

or destroy other microbes An interrelationship between two or more free-living organisms that benefits both but is not necessary for their survival Antibiosis is a form of antagonism: The production of inhibitory compounds, such as antibiotics Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 35 Biofilms: The Epitome of Synergy Biofilms are mixed communities of different kinds of

bacteria and other microbes: Pioneer colonizer initially attaches to a surface Other microbes attach to the pioneer or to the polymeric or protein substance secreted by the pioneer Quorum sensing: cells are stimulated to release chemicals as the population grows to monitor its size Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 36 Biofilms (a) Courtesy Ellen Swogger and Garth James, Center for Biofilm Engineering, Montana State University Jump to long description Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 37

The Basis of Population Growth: Binary Fission Binary fission: Parent cell enlarges Chromosomes are duplicated Cell envelope pulls together in the center of the cell to form a septum Cell divides into two daughter cells Jump to long description Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 38 The Rate of Population Growth Generation time or doubling time:

The time required for a complete fission cycle Each new fission cycle doubles the population As long as the environment remains favorable, the doubling effect can continue at a constant rate The length of the generation time is a measure of the growth rate of an organism Jump to long description Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 39 The Rate of Population Growth Exponential growth: The growth pattern of microbes Useful to express the

populations of microbes as exponents or logarithms Plotting data from a growing bacterial population: Number of cells as a function of time Can be represented logarithmically or arithmetically Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consentJump of McGraw-Hill Education. to long description 40 Growth Curve in a Bacterial Culture Jump to long description

Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 41 Stages in the Normal Growth Curve Lag phase: Flat period on the graph when the population appears not to be growing Newly inoculated cells require a period of adjustment, enlargement, and synthesis Cells are not yet multiplying at their maximum rate Population of cells is so sparse that the sampling misses them Exponential growth or log phase: Period during which the growth curve increases geometrically Phase will continue as long as cells have adequate nutrients and the environment is favorable Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 42

Stages in the Normal Growth Curve Stationary growth phase: Population enters survival mode Cells stop growing or grow slowly Death phase: Limiting factors intensify and cells begin to die at an exponential rate Curve dips downward Copyright 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 43

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