Chapter 5: Environmental influences and control of microbial growth Flashcards | Knowt (2024)

What are environmental limits on growth?

Temperature and pressure

What is true about microbes?

They have both the fastest and the slowest growth rate of organisms

What are normal growth conditions?

Sea level, temperature (20-40C), near neutral pH, and ,9% salt and ample nutrients

What are ecological niche outside the normal window called?

Extreme

What are organisms called that can inhabit extreme conditions?

extremophiles

What are extremophiles?

Microbes that are able to grow in conditions very different from those of humans

Compared to the definition of normal what were the conditions of life when it first began?

Extreme

What is the environmental habitat that a species inhabits based on?

The tolerance of that organisms proteins and other macromolecular structures to the physical conditions with that niche

What can be noted about multiple extremes?

That the environment can be met simultaneously

What is bioinformatic analysis?

When DNA sequences of a gene is used to predict the function of its protein product

What does bioinformatic analysis allow for us to do?

Study the biology of organisms that we cannot culture

What does global approaches that were used to study gene expression allow for us to do?

View how organisms respond to changes in their environment

What does knowing which genes and proteins are expressed in a given situation reveal?

It reveals how much microbes grow under different conditions and defend themselves against environmental stresses

What are microbes commonly classified by?

Their environmental niche

What does bacteria cell temperature match?

That of its immediate environment

What does changes in temperature impact?

It impacts every aspect of microbial physiology

What does every organism have?

An optimum temperature, as well as minimum and maximum temperature that defines its growth limits

When do species grow most quickly?

At temperatures where all of the cells proteins work most efficiently

When does growth stop?

When rising temperatures cause critical proteins or cell structures to fail

What is true about microbes that grow at a higher temperature?

They can achieve higher rates of growth

When does microbial growth roughly doubles?

Every 10C rise in temperature

What can microorganisms be classified by?

Their growth temperature

What is the temperature range for psychrophiles in celsius?

0-20

What is the temperature range for mesophiles in celsius?

15-45

what is the temperature range for thermophiles in celsius?

40-80

what is the temperature range for hyperthermophiles in celsius?

65-121

What is the heat shock response cased by?

Rapid temperature changes during growth that activate groups of stress response genes

What does the protein production heat shocking genes include?

Chaperones that maintain protein shape and enzymes that change membrane lipid composition

What response has been examined in all living organisms?

A heat shock response

What are organisms adapted to high pressures called?

Barophiles or piezophiles

What is true about barotolerant organisms?

They grow well over the range of 1-50MPa, but their growth falls off thereafter

Why are many barophiles considered psychrophiles?

Their average temperature at the ocean floor is 2C

What does increased hydrostatic pressure and cold temperatures reduce?

Membrane fluidity

What is water critical to?

Life

What is water activity?

A measure of how much water is available for use

How is water activity measured?

As the ration of the solutions vapor pressure relative to that of pure water

What water activity levels doe bacteria require?

>.91

What water level activities can fungi tolerate?

>.86

what is osmolarity?

A measure of the number of solute molecules in a solution and is inversely related to water activity

Why is osmolarity important?

Because of the cells semipermeable plasma membrane

What is true for a cell in a hypertonic medium?

It allows water to leave the cell in an attempt to equalize osmolarity across the membrane

What will suspending a cell un hypotonic medium cause?

An influx of water

What are aquaporins?

Membrane channel proteins that allow water to traverse the membrane much faster than by diffusion

What does aquaporin help with?

Protecting the cell from osmotic stress

How many mechanism do microbes have to minimize osmotic stress?

Two mechanisms

In hypertonic media how do bacteria protect their internal water?

By synthesizing or importing compatible solutes

In hypotonic media, what can pressure sensitive or mechanisensitive channels be used to do?

Leak solutes out of the cell

What do halophiles require?

high salt concentration from 2-5 NaCl

How do halophiles achieve a low internal concentration of Na

It uses a special ion pump to excrete sodium and replaces it with other cation

What does the concentration hydrogen ions also have a direct effect on?

The cells macromolecular structure

What will extreme concentration of either hydronium or hydroxide ion cause?

limitation of cells and the death of cells

What does living cells tolerate the greatest range of environmental concentration of?

Hydrogen

What are the three classes of bacteria differentiated by?

The pH range at which the cells grow

What pH does neutralophiles grow?

5-8

What pH does acidophilus grow?

0-5

What pH does alkaliphiles grow?

9-11

What is true about extremophiles?

An extremophile for one environmetal factor is an extremophile with respect to others as well

What is true about salty soda lakes?

They have high salt concentration and pH values as high as pH 11

What is the key to survival for alkaliphiles?

The cell surface barrier that sequesters fragile cytoplasmic enzymes away from harsh extracellular pH

What does the cell wall consist of?

Acidic polymers and excess of hexosamines in the peptidoglycan

What does the cell membrane consist of?

High levels of father lipids

What kind of force doe alkaliphiles use?

Sodium motive force and proton motive force

What happens when cells are placed in pH conditions below the optimum?

The protons can enter the cell and lower internal pH to lethal pH

How can microbes prevent unwanted influx of protons?

By exchanging extracellular K for intracellular H when the internal pH becomes too low

Under extreme conditions what can alkaline conditions do?

Use there Na/H anti porter to bring protons into the cell in exchange for expelling Na

What is it called when microbes have the ability to grow without oxygen?

anaerobes

What are microoranisms called when they have a dependence on oxygen?

Aerobes

In aerobes what do microorganism use molecular oxygen as?

A terminal electron acceptor in an electron transport system

What is areobic respiration?

When aerobes uses molecular oxygen as a terminal electron acceptor to extract energy from nutrients

What is oxygen beneficial to?

Aerobes

Is oxygen toxic to?

Aneerobes

What does reactive oxygen species do?

Efficiently destroying oxygen breakdown products

What is a characteristic of strict aerobes?

They can only grown in oxygen

What is a characteristic of microaerophiles?

Growing only at lower O2 levels

What is a characteristic of areotoleraat anaerobes?

Grows in oxygen while retaining a fermentation based metabolism

What is a characteristic of facultative anaerobes?

They can live with or without oxygen

What does both aerobes and anaerobes have the ability for?

Fermentative metabolism and respiration

What is the first technique of oxygen removal?

Special reducing agents (thioglycolate) or enzyme systems (Oxyrase) eliminate dissolved oxygen from ordinary liquid culture media.

What is the second technique of oxygen removal?

A palladium catalyst housed within a sealed anaerobe jar removes oxygen by causing it to react with hydrogen gas to form water.

What is the third step of oxygen removal?

A vacuum system removes all atmospheric gases from an anaerobic glove box so they can be replaced with a precise oxygen-free mixture of N2 and CO2

What is starvation in microbes?

A stress that can elicit a “starvation response“

What are enzymes produced to do?

Increase the efficiency of nutrient gathering and to protect cell macromolecules from damage

What is the starvation response usually triggered by?

The accumulation of small single molecules such as cAMP or guanosine tetraphosphate which globally transform gene expression

What happens with some organisms growing on nutrient limited agar?

They form colonies with intricate geometrical shapes that help the population cope in some unknown ways

What is noticed when microorganisms are severely stressed?

The bacterial population appear to sacrifice themselves to save other

How does bacteria sacrifice itself?

By undergoing programmed cell death

What happens when the bacterial cell dies?

It release nutrients that neighboring cells use to survive

What is a mechanism used for programmed cell death?

Toxin-antitoxin systems

What is an important toxin-antitoxin system in E coli?

MazE-MazF module

What does human activities have a striking impact on?

The microbial ecosystem

what is maximum diversity?

An ecosystem maintained, impart by the different nutrient gathering profiles of competing microbes

What is eutrophication?

The sudden infusion of large quantities of a formerly limiting nutrient

What leads to the bloom of microbes?

Eutrophication

What is bloom a threat to?

the existence of competing species

What are the ways that humans caused nutrient pollution?

By runoff from agricultural field, urban lawns, and golf courses. Also untreated or partially treated domestic sewage

What is another process that human will gradually alter microbial ecosystems?

By induced climate change

What is speeding up earths warming?

The heat trapping CO2 to the atmosphere by burning hydrocarbon

What is sterilization?

The killing of all living cells, spores, and viruses

What is disinfection?

The killing or removal of pathogens from inanimate objects; does not necessarily result in sterilization

What is antisepsis?

The killing or removal of pathogens from the surface of living tissue

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