Micro Midterm

MOST bacterial and archael cells are reproduced by…

binary fission

L. monocytogenes

budding

Dermocarpa

multiple fission

Streptomyces

spore formation

when must all bacteria and archaeal cells replicate and segregate their genomes

prior to division

what may increase in cellular constituents result in?

* increase in #
* increase in cell size

when is a microbial growth curve observed?

when microorganisms are cultivated in a liquid broth culture

how are batch cultures incubated?

in closed vessel with single batch of medium

how are batch cultures plotted?

cell # vs time

lag phase

cells synthesize new components

* replenish materials
* adapt to new medium
* cell replicate DNA, increase in mass, and divide

exponential phase

rate of growth and division is constant

* population most uniform (in terms of chem and phys properties)

what does exponential phase growth rate depend on?

nutrient availability

final net growth increases with…

initial amount of limiting nutrient present

growth rate increase with…

nutrient concentration

stationary phase

total # of viable cells remains constant

* balance btwn cell division and death
* population cease to divide but could be metabolically active

what happened in a closed system?

growth eventually ceases

reasons for stationary phase?

* nutrient limitation
* limited oxygen availability
* toxic waste accumulation
* critical population density reached

death phase

\# off viable cells decline exponentially (cells die at constant rate)

what causes irreparable harm to cells?

nutrient deprivation and build up of toxic wastes

long-term stationary phase

bacterial population continually evolves

what is long-term stationary phase marked by?

successive waves of genetically distinct variants

in long-term stationary phase natural selection occurs within…

single culture

what is generation doubling time?

time required for population to double in size

what does generation doubling time depend on?

the species of microorganism and environment

MOST organisms grown in…

fairly moderate environmental conditions

where do extremophiles grow?

under harsh conditions that would kill most organisms

ALL microbes respond to…

changes in their environments

microbes have optimal range of…

an environmental parameter for best growth

what can changes in osmotic concentrations in environments do?

can effect microbial changes

hypotonic

lower solute concentration outside the cell (water enters, cell explodes)

hypertonic

higher solute concentration outside the cell than inside (water leaves, cell shrinks)

MOST microbes live in a…

hypotonic enviornment

what do mechanosensitive (MS) channels in plasma membrane do?

allow solutes to leave (assists to lower solute concentration of cytoplasm)

what do protists use to expel excess water?

contractile vacuoles

halophiles

require NaCl at a concentration above 0.2M

extreme halophiles

require salt concentrations between 3M and 6.2M

salt-in

* accumulates K + Cl in cytoplasm
* proteins need high salt levels

salt-out

* keep salt ions outside cell
* synthesize compatible solutes that don’t interfere with growth

water activity (Aw)

measure of the degree of water availability

what does low water activity mean?

most water is bound and not available to microorganisms

most microorganisms only grow well at water activates around

0\.98

osmotolerant

microorganisms that can grow over wide ranges of water activity but optimally at higher levels

xerotolerant

microbes that withstand high solute concentrations

acidophiles

show growth best between 0-5.5 pH

alkaliphiles (alkalophiles)

show growth best between 8-11.5 pH

Most bacteria and protists are…

neutrophils

MOST fungi prefer…

more acidic surroundings (4-6 pH)

photosynthetic protists also seem to favor….

slight acidity

SOME archaea are…

acidophiles

alkaliphiles are distributed among…

all the domains of life

how do microorganisms respond to external pH changes?

using mechanisms that maintain a neutral cytoplasmic pH

pump protons (H+) out of the cell

acidophiles

exchange internal Na+ ions for external protons

alkaliphiles

can microbes regulate their internal temperature?

no

what happens when an enzyme is below optimal temp?

the enzyme is not catalytic

what can high temperatures inhibit?

enzyme functioning and can be lethal

what are the cardinal temperature?

* minimum
* maximum
* optimal

psychrophiles

0-20 degrees C

psychrotrophs

0-35 degrees C

mesophiles

20-45 degrees C

thermophiles

45-85 degrees C

hyperthermophiles

85-100 degrees C

how is protein structure stabilized?

* more H bonds
* more proline (less flexible peptides)
* chaperones aid in folding

how are membranes stabilized?

* more saturated, more branched, and higher Molec weight
* ether linkages (resistant to hydrolysis)

what does growth in presence of different oxygen concentrations depend on?

* microbe’s metabolic processes
* electron transport chains (ETC)
* terminal electron acceptor used

obligate aerobe

requires O2

obligate anaerobe

usually killed in presence of 02

microaerophile

requires 2-10% O2

facultative anaerobes

don’t require O2 but grow better in its presence

aerotolerant anaerobes

grow with or without O2

oxygen reduces to…

reactive oxygen species (ROS)

what are the types of reactive oxygen species (ROS)?

* superoxide radical
* hydrogen peroxide
* hydroxyl radical

what are the protective enzymes that aerobes produce?

* superoxide dismutase (SOD)
* catalase
* peroxidase

microbes that live on land and water surface live at a pressure of…

1 atmosphere (atm)

where do SOME bacteria and archaea live?

in deep sea with very high hydrostatic pressures

barotolerant

adversely affected by increased pressure, but not as severely as non tolerant organisms

peizophilic (barophilic)

requires high pressure for growth

* change membrane fatty acids to adapt to increasing pressure (lipids become more unsaturated and shorter)

sessile

microbes grow attached to surfaces

planktonic

free floating

MOST microbes are…

sessile

biofilm

slime enclosed communities of microbes

where are biofilms ubiquitous in nature?

in water

what do microbes do to form extracellular polymeric substances (EPS)?

* reversibly attach to conditioned surfaces
* release polysaccharides, proteins, and DNA

at what point are additional polymers produced in biofilm formation?

* as microbes reproduce and biofilm matures

what do physiological changes and EPS protect microbes from?

harmful agents (ex. UV)

what occurs when biofilm is formed on medical devices?

antibiotic treatment fails

biocide

antimicrobial agents that control microorganisms

What is N-acylhomoserine lactone (AHL)?

* autoinducer
* moves across plasma membrane from the cytoplasm to outside of the cell

what occurs when cell population is high?

AHL diffuses in the cell, inducing specific gene expression

auto inducing peptides (AIPs)

* gram positive bacteria
* auto inducing short peptides

**Sterilization**

process by which all living cells, spores, and acellular entities are destroyed or removed from an object

(Sterilant is the chemical agent)

**Disinfection**

killing, inhibition, or removal of disease-causing microorganisms

(does not always sterilize as spores or a few organisms can remain)

**Disinfectants**

agents, usually chemical, used for disinfection, usually used on inanimate objects

**Sanitization**

reduction of microbial population to levels deemed safe by public health standards

**Antisepsis**

destruction of microbes on living tissue

**Antiseptics**

chemical agents applied to tissue to kill or inhibit growth of pathogen

**Chemotherapy**

generic term that describes application of chemicals to kill microorganisms

what do cidal agents do?

kill

what do static agents do?

inhibit growth

what groups cidal agents kill?

**bactericides**, **fungicides**, and **viricides**