Elements of Microbial Nutrition, Ecology and

Growth

Chapter 7

Microbial nutrition

____________: process by which chemicals (nutrients) are acquired from environment and used by organism

________________________: must be provided; can be in elemental or molecular form

Elements needed for life ________________ Ca Fe Na Cl Mg and some others

Nutrients ____________– required in large quantities;

principal roles in cell structure & metabolism • proteins, carbohydrates

____________or trace elements – required in small amounts; involved in enzyme function & maintenance of protein structure• manganese, zinc, nickel

Microbial nutrition

Nutrients ____________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

____________nutrients- contain ____________and ____________atoms and are usually the products of living things

• methane (CH4), carbohydrates, lipids, proteins, and nucleic acids

Microbial nutrition

Microbial nutrition

Chemical composition of cytoplasm

70% water proteins 96% of cell is composed of 6 elements

• ____________

• ____________

• ____________

• ____________

• ____________ See Table 7.2 for E. coli

Microbial nutrition

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How do organisms obtain carbon? ____________– an organism that must

obtain carbon in an organic form made by other living organisms (proteins, carbohydrates, lipids and nucleic acids)

____________- an organism that uses CO2, an inorganic gas as its carbon source• not dependent on other living things

- 6 major elementsMicrobial nutrition

Nitrogen Main reservoir is nitrogen gas (N2) 79% of earth’s atmosphere is N2

Nitrogen is part of the structure of proteins, DNA, RNA & ATP – these are the primary source of N for heterotrophs

Some bacteria & algae use inorganic N nutrients (NO3

-, NO2-, or NH3)

Some bacteria can fix N2

Regardless of how N enters the cell, it must be converted to NH3, the only form that can be combined with carbon to synthesis amino acids, etc.

6 major elements

Oxygen

O2 makes up ______% of atmosphere essential to metabolism of many organisms major component of carbohydrates, lipids and

proteins plays an important role in structural &

enzymatic functions of cell component of inorganic salts (sulfates,

phosphates, nitrates) & water

6 major elements

Hydrogen

major element in all organic compounds & several inorganic ones (water, salts & gases)

gases are produced & used by microbes roles of hydrogen

• maintaining ________

• forming H bonds between molecules

• serving as the source of free energy in oxidation-reduction reactions of respiration

6 major elements

Phosphorous

main inorganic source is phosphate (PO4-3)

derived from phosphoric acid (H3PO4) found in rocks & oceanic mineral deposits

key component of ____________, essential to genetics

serves in energy transfers (ATP)

6 major elements

Sulfur

widely distributed in environment; rocks, sediments contain sulfate, sulfides, hydrogen sulfide gas and sulfur

essential component of some vitamins and the amino acids: methionine & cysteine

contributes to stability of proteins by forming disulfide bonds

6 major elements

Important mineral ions

Potassium Sodium Calcium Magnesium Iron

Growth factors

organic compounds that cannot be synthesized by an organism & must be provided as a nutrient (essential ____________ nutrient)• essential amino acids – 20 – obtained from

food

• vitamins

How microbes feed

Nutritional type is based carbon and energy sources

Example: ____________: use inorganic carbon

(CO2)• Photoautotrophs – make their own energy

using light (“photo”)

• Chemoautotrophs – Make their own energy using chemicals rather than light

terminology

Prefixes Troph- food,

nourishment Auto- self Hetero- other Photo- light Sapro- rotten Halo- salt Thermo- heat Psychro- cold Aero- air (O2)

Suffixes: -phile to love -obe to live -troph food

examples: Autotroph Chemoautotroph Halophile, thermophile Aerobe, saprobe Aerophile (aerophilic)

How microbes feed

Facultative vs. obligate

____________– organism is able to adapt to a wide range of metabolic conditions – therefore it can facultatively switch its niche, habitat, nutrition etc.

____________or strict – has a narrow niche, habitat due to limitations in its nutrition or metabolism. Microbe can only grow under those conditions.

How microbes feed

Carbon source

Energy source

photoautotrophs CO2 ____________

chemoautotrophs CO2 Simple inorganic ____________

photoheterotrophs organic ____________

chemoheterotrophs organic Metabolizing organic ____________

How microbes feed PRINT FULL SIZE

examples

____________– • Photoautotrophs – photosynthesis6CO2 + 12H2O + light energy C6H12O6 + 6O2 + 6H2O

• Chemoautotrophs – methanogens

4H2 + CO2 CH4 + 2H2O

____________

• ChemoheterotrophsC6H12O6 + 6O2 6CO2 + 6H2O + energy

How microbes feed

____________– decompose dead organisms, recycle elements, release enzymes to digest materials

____________– utilize tissues and fluids of a living host and cause harm

parasites and saprobes can be facultative (opportunistic pathogen) or obligate

How microbes feed

saprobes

• Cannot engulf large particles of food

• Substrate is digested _________ by secreted enzymes

• Small molecules are transported into cell

How microbes feed

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How microbes feed

Symbiosis Means “________________________” Organisms (____________) have close association

1. ____________=obligatory, both symbionts benefit• Termite gut flagellates

2. ____________=commensal receives benefit, symbiont (host) is neither harmed nor benefited• satellitism, commensal intestinal bacteria (normal microbial

flora)

3. ____________= parasite benefits, host is harmed• Intestinal helminths, Rickettsia, all viruses

How microbes live

Non-symbiotic microbial associations

organisms are free-living; relationships not required for survival• ____________– members cooperate and

share nutrients

• ____________– some members are inhibited or destroyed by others

How microbes live

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Ecological Associations Among Microorganisms

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Interrelationships Between Microbes and Humans

Human body is a rich habitat for symbiotic bacteria, fungi, and a few protozoa - normal microbial ____________

Commensal, parasitic, and synergistic relationships

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Microbial Biofilms

____________result when organisms attach to a substrate by some form of extracellular matrix that binds them together in complex organized layers

Dominate the structure of most natural environments on earth

Communicate and cooperate in the formation and function of biofilms – quorum sensing

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Figure 7.13

How do microbes get their nutrients??

What are the transport mechanisms used to import nutrients and export waste?

REMEMBER: Transport occurs across the ________________________…even in microbes with cell walls, all that is going in or coming out must cross the cell membrane

transport mechanisms

1. ____________– require no energy input from cell (uses laws of physics, like entropy)

2. ____________– require energy input from cell

Transport mechanisms

Passive transport –do not require energy, substances exist in a gradient and move from areas of higher concentration towards areas of lower concentration• ____________

• ____________– diffusion of water

• ________________________– requires a carrier

concentration Amount solute/solvent

• Solute can be solid, liquid, gas

• Solvent is usually liquid Percentage = ________________________

• Examples: 3% NaCl = 3 g in 100 mL = 0.3 g/L Molarity = ________________________

• Examples: 1 M NaCl solution, 10 M glucose solution etc. Tonicity: ____________> ____________in terms

of amount of solute. ____________means both solutions have the same amount of solute.• Examples:

• 10% NaCl is more hypertonic than 1% NaCl

• 1 M glucose is more hypotonic than 5 M glucose

diffusion

• Molecules move along gradient:

• High low concentration

• Due to RANDOM motion – increased by heat (entropy)

• Evidence: Brownian movement

Diffusion in cells

Small, nonpolar molecules can diffuse across cell membrane (oxygen, small lipids)

Polar molecules – ____________ ________________________ (facilitated diffusion – still PASSIVE transport – using energy of gradient)

Passive transport

Facilitated diffusion Carrier proteins embedded in membrane Specific for a single type of molecule Saturation can occur (all binding sites on

carrier proteins are occupied by molecule being transported)

Competition – similar molecules can compete for binding sites – one with higher affinity (or concentration) will win and be transported

Passive transport

Facilitated diffusion

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osmosis• ________________________

________________________

(therefore SOLUTE cannot diffuse – so water moves instead)

• WATER moves from High low water conc. (essentially, water moves from low SOLUTE to high SOLUTE)

• Water moves from ______________________________

______________________________

Pa

ssive tra

nsp

ort

Tonicity and osmosis

____________– low solute (high water) – has LOW osmotic potential (LOW osmotic pressure). PURE WATER is the most hypotonic

____________– high solute (low water) – has HIGH osmotic potential (pressure). Concentrated solutions (salt and sugar preservatives) are highly hypertonic.

Passive transport

Adaptations to osmotic effects

In a hypotonic environment: Bacteria, algae have cell walls so they won’t

burst – they just become ____________. Amoebas, ciliates have contractile vacuoles

constantly pumping water OUT In a hypertonic environment: Halobacteria actually absorb salt to try and

stay isotonic so they won’t LOSE water (ex. Dead sea, Great Salt Lake)

Passive transport

____________transport – requires ____________ and carrier proteins, gradient ____________• Examples: against gradient, faster than diffusion, large,

charged molecules that can’t go through membrane – all require energy

• Carrier-mediated active transport (permeases/ pumps)

• Group translocation – transported molecule chemically altered

• Bulk transport – ______________________

______________________________________

Transport mechanisms

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Carrier mediated active transport

Group translocation

See Na/K pump movie

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Bulk transport (________________) – involves vacuole/vessicle formation

Active transport

Large particles, whole cellsAmoeba

Liquids, solutionsapicomplexans

Active transport

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MICROBIAL GROWTH

Microbial growth

1. Environmental influences on growth

2. Biology – stages of growth

1. Environmental influences on microbial growth

temperature oxygen requirements pH electromagnetic radiation barometric pressure

a. Temperature:3 cardinal temperatures

Minimum temperature – lowest temperature that permits a microbe’s growth and metabolism

Maximum temperature – highest temperature that permits a microbe’s growth and metabolism

____________temperature – promotes the fastest rate of growth and metabolism

Environmental influences

3 temperature adaptation groups

1. __________________– optimum temperature below 15oC, capable of growth at 0oC

2. ________________– optimum temperature 20o-40oC, most human pathogens

3. ________________– optimum temperature greater than 45oC

Environmental influences

3 temperature adaptation groupsEnvironmental influences

Thermus aquaticus

DNA polymerase (known as Taq polymerase) used in PCR (polymerase chain reaction)

________________(1983) – Nobel Prize in Chemistry - 1993

Enzyme is HEAT STABLE – so during cycling of the PCR machine (95-55-77°C) it does not get destroyed

Huge advance in biotechnology

b. Oxygen requirements

Depends on whether cell can handle toxic byproducts (superoxide, peroxide)

________________________________ ________________________________

Environmental influences

Aerobes vs. anaerobes ______________– grown in normal O2,

can handle by-products. Some are facultative anaerobes. Microaerophile – cannot grow under anaerobic conditions, but can handle some O2.

________________–

• strict – die in presence of O2.

• Aerotolerant – cannot perform aerobic respiration, but are not killed by O2

Environmental influences--Oxygen requirements

_____________________ broth – absorbs O2 from airEnvironmental influences

Aerobic (Pseudomonas)

Facultative anaerobe (Staph aureus)

Facultative anaerobe (E. coli)

Obligate anaerobe (Clostridium)

Anaerobic environmental chamber

Anaerobic jar – uses gas packs that provide a defined atmosphere

O2 removed from atmosphere + H2 water

Also used for ________________

c. pH, pressure and EM radiation pH – majority grow between 6-8

• Acidophiles, Alkalinophiles

Osmotic pressure – most are in hypotonic or isotonic • Osmophiles/halophiles – grow in hypertonic (high

osmotic pressure); can cause food spoilage

Hydrostatic pressure – barophiles (deep sea) EM radiation – UV and ionizing rays are used in

microbial control. Damage DNA.

Environmental influences

2. Biology of microbial growth

a. Cell division – binary fission b. Population growth rate

• Generation/doubling time

• Growth curve – stages

c. Methods for analyzing growth

a. ______________________– dividing in twoBiology of microbial growth

b. Population growth rate: Exponential growth

Nf = total number of cells at some point

Ni = starting number of cells

n = generation number

= elapsed time / generation time (t/gen)

2n = number of cells in that generation

Biology of microbial growth

b. Population growth curve

Shows growth progress over a time period #cells/time

Steps:1.Inoculate culture and incubate

2.Sample (volume) at time intervals

3.Plate onto solid media4.Count number of cells (get #cells/volume)

Biology of microbial growth

b. Stages of Growth curve

Biology of microbial growth

Growth curve1. ________ phase – “flat” period of adjustment,

enlargement; little growth

2. ____________ growth phase – a period of maximum growth will continue as long as cells have adequate nutrients & a favorable environment

3. ______________ phase – rate of cell growth equals rate of cell death cause by depleted nutrients & O2, excretion of organic acids & pollutants

4. ___________ phase – as limiting factors intensify, cells die exponentially in their own wastes

Biology of microbial growth

Importance of growth curve

Antimicrobials – more effective on exponential phase

Infectivity – early, middle stages – more likely to pass microbe to others

Course of infection – fast growing microbes can overwhelm host defenses

Biology of microbial growth

c. Methods for analyzing growth

1. Inoculate culture

2. Count cells• ________________– use spectrophotometer• ________________

• Direct, total cell count (hemocytometer)

• Viable plate count (look at CFUs)

• Coulter counter/Flow cytometer

Turbidity

Biology of microbial growth

Enumeration - Direct microscopic count

Biology of microbial growth

Enumeration - Electronic countingBiology of microbial growth