BIOS 3220 Exam 2

Eukaryotic microbe reproduction

haploid or diploid, asexual and sexual

Bacterial and archaeal reproduction

binary fission, budding, filamentous

Binary fission

Asexual reproduction in prokaryotes, involves DNA replication, septum formation, cytokinesis

Septum

a partition that forms during cell division to divide two daughter cells

exponential growth

growing bacterial population doubling at regular intervals

generation time

Time it takes for a microbial population to double (g)

Growth rate

number of generations per hour (k)

bacterial cell cycle

DNA replication and partition, septum formation and cytokinesis

Bacterial and archaeal chromosomes

circular

Origin of replication

Site at which replication of a chromosome begins

Terminus

Site at which replication of a chromosome stops, opposite of origin in location

replisome

group of proteins needed for chromosome replication

Replication forks

Y shaped structure where DNA is replicated

bidirectional replication

DNA replication goes in both directions from the origin

origin partition

origins moving to opposite ends of the cell during DNA replication

Chromosome partitioning

replisome performs condensation- pulling of chromosomes to opposite ends

MreB

actin homolog, determines prokaryotic cell shape, involved in chromosome separation

Septation

formation of cross walls between daughter cells

Steps of septation

Site selection, z ring assembly, cell wall synthesizing machinery assembles, constriction of cell, septum formation

FtsZ

tubulin homolog in prokaryotes, polymerized into Z ring

Z ring

links to plasma during septation, FtsZ polymer

MinCDE system

limits Z ring to center of cell, proteins oscillate between ends of cell

MinC

blocks Ftz binding, activated by MinD and blocked from center by MinE

Divisome

cell wall synthesis components assemble at z ring

Septal wall synthesis

divisome assembles, z ring constricts invaginating plasma membrane, uses GTP

FtsA and ZipA

link Z ring to plasma membrane

ZepA and ZepB

signal FtsZ when chromosome has been replicated

Autolysins

enzymes that degrade peptidoglycan in a controlled manner, cleave between NAM and NAG

Transpeptidases

peptidoglycan peptide side chain crosslinking enzymes, also called penicillin binding proteins

penicillin binding proteins

transpeptidases, become inactive after binding penicillin

Cocci cell wall growth

new peptidoglycan only forms at central septum

Rod cell wall growth

Peptidoglycan formed in helices across cell length, facilitated by MreB

Vibrio cell wall formation

Uses FtsZ, MreB, and crescentin, side with crescentin is shorter

Crescentin

forms shape in vibrio bacteria, localized to one side, slows peptidoglycan formation

Extremophiles

organisms that grow in harsh conditions intolerable by most organisms

Hypotonic solution

lower osmotic concentration outside the cell, risk of bursting

Hypertonic solution

higher osmotic concentration outside the cell, risk of plasmolysis

microbe hypotonic adaptation

reduce osmotic concentration of plasma through mechanosensitive channels in membrane

microbe hypertonic adaptations

`increase internal solute concentration, use solutes compatible with metabolism and growth

Halophiles

grow optimally in the presence of .2M NaCl

Extreme halophiles

require salt concentrations of 2-6.2M, very high potassium concentrations

Halotolerant

can grow under elevated salt conditions but do not require high salt for growth

pH

negative log of hydrogen ion concentration, most organisms maintain neutral internal

acidophiles

optimum growth between o and 5.5 pH, plasma membrane impermeable to protons

neutrophiles

growth optimum between 5.5 and 7 pH

alkaliphiles

growth optimum between 8.5 and 11.5 pH

Acid tolerance response

pump protons out of cell using ATP, synthesize acid and heat shock proteins that protect cytoplasmic proteins

Enzymes and temperature

limits the temperatures microbes can grow in, activity decreases with change

psychrophiles

microbes with optimal growth at 0 -20 C

psychrotrophs

microbes with optimal growth at 0 - 35 C

mesophiles

microbes with optimal growth at 20 - 45 C

thermophiles

microbes with optimal growth at 55- 85 C

Hyperthermophiles

microbes with optimal growth at 85 - 113 C

Thermophiles adaptations

stabilized protein structure, histones stabilize DNA, increased saturated, high weight, ether linked membrane lipids

Thermophile proteins

More H bonds, more proline, more chaperones

Aerobe

grows in presence of 20% oxygen

Obligate aerobe

Requires oxygen to live

Anaerobe

grows in the absence of oxygen

Obligate anaerobe

cannot survive in presence of oxygen, lack superoxide dismutase and catalase

Microaerophiles

requires 2-10% oxygen

facultative anaerobes

if necessary can grow without oxygen, grows better with oxygen

Aerotolerant anaerobes

grow equally well with or without oxygen

oxic

environment with present dissolved oxygen

anoxic

environment depleted of dissolved oxygen

reactive oxygen species

reduced oxygen - superoxide radical, hydrogen peroxide, hydroxyl radical

aerobe enzymes

neutralize reactive oxygen species, superoxide dismutase, catalase, peroxidase

barotolerant

adversely affected by increased pressure, still somewhat tolerant

Barophilic

require or grow more rapidly under high pressure, adapted membrane fatty acids

Ionizing radiation

X rays and gamma rays, disrupts chemical structure of DNA

Deinococcus radiodurans

polyextremophile, can withstand ionizing radiation, cold, dehydration, acid, vacuum due to protected DNA repair mechanisms and multiple genome copies

Ultraviolet radiation

absorbed by DNA and causes damage, 260 nm

Visible light damage

Creates singlet oxygen at high intensities

Carotenoid pigments

Protect bacteria from light induced photooxidation

microbial low nutrient adaptations

endospore formation, metabolic dormancy, persister cells, biofilms

Biofilms

community of microorganisms and extracellular polymeric substances, matrix protects, difficult to kill, can cause persistent infections

Biofilm matrix

Polysaccharides, proteins, DNA

conditioned surface

acellular area with high nutrients, biofilms tend to grow

Biofilm heterogeneity

May contain multiple species, different areas exposed to different conditions, creates varying metabolic activity

Quorum sensing

Density dependent biofilm communication, detects concentration of autoinducer to alter gene expression and alter number of cells in biofilm

Autoinducer

signaling molecule released by biofilm for quorum sensing

N-acyl-homoserine lactones (AHLs)

autoinducer molecules in gram negative bacteria

Autoinducer peptides (AIPs)

autoinducers in gram positive bacteria

processes regulated by quorum sensing

symbiosis, pathogenicity and increased virulence factor production, DNA uptake for antibiotic resistance genes

Culture media

solid or liquid, contains all nutrients required by organism for growth, classified based on chemical constituents, physical nature, function

chemical /physical types of culture media

chemically defined and complex

Chemically defined culture media

chemical composition known

Complex culture media

chemical composition somewhat unknown

Peptones

protein hydrolysates/fragments from digested proteins

Extracts

aqueous, usually beef or yeast

agar

polysaccharide used to solidify liquid media- cannot be degraded by most microorganisms

Media components

agar, extract, peptones

functional media types

supportive and enriched

Supportive media

general purpose, support growth of many microorganisms

Enriched media

general purpose media supplemented with something else

Selective media

favors the growth of some microorganisms, inhibits the growth of others, MacConkey agar

Differential media

distinguish between microorganisms based on biological characteristics, blood and MacConkey agar

Aerobe cultivation

liquid cultures shaken, increases rate of growth

Anaerobe cultivation

uses gaspak system

Culture isolation

spread plate, streak plate, pour plate techniques to generate single colonies arising from single cells

Streak plate

spreading mixtures of cells on an agar surface to separate individual cells, uses bacteriological loop