Microbiology Exam 2 - Collins

treatment for plague

- gentamicin - streptomycin

catabolism

- the breakdown of macromolecules into simple compound parts - releases energy

what conditions do most organisms grow in?

fairly moderate environmental conditions

barotolerant

negatively affected by increased pressure

quorum sensing with gram-

- acylhomoserine lactone (AHL) is an autoinducer molecule produced by many gram negative organisms

classes of growth factors

- amino acids (protein synthesis) - purines and pyrimidines (nucleic acid synthesis) - vitamins (enzyme cofactors) - heme

reproductive strategies of eukaryotic microbes

- asexual/sexual - haploid/diploid

lag phase

- cell synthesizing new components - varies in length - ex: to replenish spent materials; to adapt to new medium

stationary phase

- closed system population growth eventually ceases (total number of viable cells remain constant) - active cells stop reproducing or reproductive rate = death rate

biofilms

- complex, slime enclosed community of microbes - microbes attach to surfaces (sessile) or just "free float" (planktonic) - ubiquitous (everywhere) in nature - exchanges take place metabolically (DNA uptake and communication) btw organisms

chemical requirements (nitrogen)

- component of proteins, DNA, ATP - most bacteria decompose protein for the nitrogen source - use N2 in nitrogen fixation

acylhomoserine lactone (AHL)

- diffuses across plasma membrane - induces expression of target genes that regulate a variety of functions

yersinia pestis (microbe of the week)

- discovered by Alexandre yersin - causes the plague - transmitted thru flea bites and contaminated fluid/tissue

differential media

- distinguish between different groups of microbes based on biological characteristics - ex: blood agar (hemolytic vs non-hemolytic)

effect of pH and temp. on enzymes

- each enzyme has an optimal pH and temp. - denaturation - loss of enzyme's strx and activity when temp. and pH are not optimal

electron transport chain

- electron carriers organized into the ETC with the first electron carrier having the most negative standard redox potential - potential energy stored in first redox couple is released and used to form ATP

vibrio cholerae growth conditions

- facultative anaerobe - marine and estuarine environments

selective media

- favors growth of some microbes and inhibits growth of others - ex: MacConkey agar selects for gram- bacteria

Vibrio Cholerae (microbe of the week)

- gram- - curved/rod shaped - one or more flagella - quorum sensing

yersinia pestis (cont.)

- gram- - facultative anaerobe

reproductive strategies of prokaryotic microbes (bacteria and archaea)

- haploid - asexual (binary fission)

role of ATP in metabolism

- high energy molecule - exergonic breakdown of ATP is coupled with endergonic rxns

hypertonic solution

- higher osmotic concentration - water exits cell - membrane shrinks from cell wall (plasmolysis)

quorum sensing

- how bacterial cells communicate in a density-dependent manner - processes regulated by quorum sensing involve host-microbe interactions

How do enzymes lower activation energy?

- increase concentrations of substrates at active site of enzyme - orient substrates properly with respect to each other in order to form the transition-state complex

cholera

- infectious gastroenteritis (severe diarrhea) - from ingesting contaminated food/water - transmitted person to person

electron carriers? location? examples?

- located in plasma membranes of chemoorganotrophs in bacteria and archaea cells (prokaryotic) - located in intermal mitochondrial membranes in eukaryotic cells - ex: NAD, NADP, cytochromes

hypotonic solution

- lower osmotic concentration - water enters cell - cell swells/burst

pH

- measure of relative acidity of a solution - pH = -log[H+]

effect of temp. on microbial growth

- microbes cannot regulate internal temp. - enzymes have optimal temp. at which they function best - too high temp. can inhibit enzymes

effect of pH on microbial growth

- microbes maintain an internal pH near neutrality

biofilm formation process

- microbes reversibly attach to conditioned surface and release polysaccharides, proteins, and DNA to form the extracellular polymeric substances (EPS) - additional polymers are produced as microbes reproduce and biofilm matures

reasons for stationary phase

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

growth curve

- observed when microbes are cultivated in batch culture - plotted as log of cell number vs time - 4 phases (lag, exponential, stationary, death)

growth factors

- organic compounds - essential cell components that the cell cannot synthesize - must be supplied by environment

aerobic respiration

- process that produces ATP - uses 3 pathways (glycolysis, TCA cycle, ETC w O2 as final e- acceptor)

purpose of EPS and additional polymers?

- protects microbes from harmful agents - ex: UV light , antibiotics, antimicrobials

temp. ranges for microbial growth

- psychrophiles - 0 to 20 C - psychotrophs - 0 to 35 C - mesophiles - 20 to 45 C - thermophiles - 55 to 85 C - hyperthermophiles - 85 to 113 C

exponential phase

- rate of growth and division is constant and maximal

extreme halophiles

- require >2 M NaCl

barophilic

- require or grow faster in the presence of increased pressure - change membrane fatty acids to adapt to high pressure

bacterial cell cycle

- sequence of events from formation of new cell through next cell division - 2 pathways function during cycle (DNA replication/partition and cytokinesis)

role of enzymes in rxns

- speed up the rate of rxn - does this by lowering the activation energy

what do strict anaerobic microbes lack or have low quantities of?

- superoxide dismutase (SOD) - catalase

quorum sensing host-microbe interaction examples

- symbiosis - Vibro fischeri and bioluminescence in squid - pathogenicity and increased virulence factor production - DNA uptake for antibiotic resistance genes

anabolism

- the build up of macromolecules by combining simpler molecules - uses energy

metabolism

- the total of all chemical reactions in the cell - 2 parts (catabolism and anabolism)

halophiles

- thrive in high salt concentrations - grow optimally at >0.2 M NaCl

generation (doubling) time

- time required for population to double in size

oxidation-reduction rxns (redox)

- transfer of e- from a donor to acceptor

most susceptible to cholera?

- type O blood (type AB least susceptible) - weakened immune system - decreased gastric acidity - malnourished

chemical requirements (phosphorus)

- used in DNA, RNA, ATP - found in membranes

chemical requirements (sulfur)

- used in amino acids, thiamine, and biotin

treatment for cholera

- water/electrolyte replacement - antibiotic therapy (tetracycline)

chromosome replication and partitioning

-Most bacterial chromosomes are circular -Single origin of replication - site at which replication begins -Terminus - site at which replication is terminated, located opposite of the origin -Replisome - group of proteins needed for DNA synthesis -DNA replication proceeds in both directions from the origin -Origins move to opposite ends of the cell

microbial nutrition

Section 1

increase in cellular constituents results in?

increased cell number and size

defined or synthetic media

all components and their concentrations are known

Oxygen Effects on Microbial Growth

anaerobic and aerobic

carbon purpose in microbial nutrition?

carbon is backbone of all organic components present in cell

relationship between catabolic and anabolic reactions

catabolism fuels the next anabolic reaction

mechanical work

cell motility and movement of structures within cells

how does solute and water activity affect growth?

changes in osmotic concentrations in the environment affects microbial cells

complex media

contain some ingredients of unknown composition and/or concentration

heterogeneity

differences in metabolic activity and locations of microbes

facultative anaerobes

do not require O2 but grow better in its presence

3 growth rates in terms of temp. (shown on a curve)

minimum, optimum, maximum

are endergonic rxns spontaneous?

no, because K < 1

what does bacterial growth refer to?

population growth NOT growth of individual cells

peptones

protein hydrolysates prepared by partial digestion of various protein sources

substrate

the reacting molecule

electrons purpose in microbial nutrition?

electrons play a role in energy production and reduction of CO2 to form organic molecules

hydrogen and oxygen purpose in microbial nutrition?

found in organic molecules

aerotolerant anaerobes

grow equally with or w/out O2

acidophiles

grow optimally between pH 0-5.5

neutrophiles

grow optimally between pH 5.5-7

alkalophiles

grow optimally between pH 8.5-11.5

extremophiles

grow under harsh conditions that would kill most other organisms

anaerobe

grows in absence of O2

obligate anaerobe

grows in absence of O2; usually killed in presence of O2

aerobe

grows in presence of atmospheric oxygen (20% O2)

death phase

- 2 hypotheses 1) cells Viable But Not Culturable (VBNC) - cells alive but dormant capable of growth when conditions are right 2) programmed cell death

macro elements (macronutrients)

- C, O, H, N, S, P, K, Ca, Mg, Fe - Required in relatively large amounts

micronutrients (trace elements)

- Mn, Zn, Co, Mo, Ni, Cu - required in small amounts; involved in enzyme function and maintenance of protein structure (manganese, zinc, nickel)

quorum sensing with gram+

- S. pneumoniae - produce small proteins that increase in concentration as microbes replicate and convert to a competent state - DNA uptake occurs and bacteriocins are released

ETC (cont.)

- Series of carrier molecules that pass electrons from one to another to final electron acceptor -Energy from electrons used to pump protons (H+) across the membrane, establishing a proton gradient - Located in inner mitochondrial membrane of eukaryotes & in cytoplasmic membrane of prokaryotes - e- flow from carriers w more negative standard redox potential to carriers w more positive

what is the standard redox potential?

- a measure of the tendency of the reducing agent to lose e- - more negative redox potential = better e- donor - more positive redox potential = better e- acceptor

3 types of microbial work

1) chemical work 2) transport work 3) mechanical work

when is a reaction at equilibrium?

rate of forward rxn = rate of reverse rxn

microaerophiles

require 2-10% O2

obligate aerobe

requires O2 for growth

Environmental Factors Influencing Growth

section 2

Microbial Metabolism

section 3 - look over slides cause a lot of them are hard to make flashcards on

are exergonic rxns spontaneous?

si, because K > 1

catalyst

substance that increases the rate of rxn w/out being permanently altered

agar

sulfated polysaccharide used to solidify liquid media

chemical work

synthesis of complex molecules

transport work

take up of nutrients, elimination of wastes, and maintenance of ion balances

autotrophs

use CO2 as their sole or principal carbon source

heterotrophs

use organic molecules as carbon sources which often also serve as energy source