Microbiology Exam One

why do we care about microbes

maintain earth's ecological balance

some are used to produce food and chemicals

some are needed to maintain good health

some cause disease to humans, plants, or animals

how do microbes maintain earth's ecological balance

geochemical recycling, recycle water

how are microbes used to produce food and chemicals

fermentation products, alcohol

how are microbes needed to maintain good health

food digestion, prevention of pathogen growth, vitamin production

how do some microbes cause disease to humans plants or animals

infectious diseases, biofilms

how would the world be different without microbes

biogeochemical cycle would cease, humans would need to fix and distribute nitrogen for crop production, most species would go extinct, it would take us nearly a week to recognize what had happened, starvation and biogochemical asphyxiation

prokaryote

no true nucleus

what is the problem with the term prokaryote

refers to both bacteria and archae, archae are actually most closely related to eukaryotes

what did carl woese do and how has it changed out understanding of the tree of life

analyzed ribosomal RNA, determined there are three domains of life: bacteria, archaea, eukarya

three main groups of archaea

methanogens, thermophiles, halophiles

significants of lynn margulis

revived endosymbiotic theory after the discovery of mitochondiral and choloroplast DNA

endosymbiiotic theory

mitochondria and chloroplasts arose after being engulfed by a eukaryotic host and established a symbiotic relationship

cell morphology

cell shape

cell arrangement

how cells are organized

how do bacteria maintain their size and shape

their cell wall

hypertonic environment cause

plasmolysis

hypotonic solutions cause

lysis

which bacterial cell component has the highest percentage of total weight

water

why are there approximately two copies of DNA

because it replicates its genome before splitting

why are there two times as many different kinds of proteins as RNAs

bacteria are polycistronic

polycistronic

a single RNA contains the genetic information to code for multiple different proteins

functions of cell membrane

selective permeability

maintain ion gradients

anchor proteins

contain enzymes for ATP production

amphipathic

Possess both polar and nonpolar ends

what advantage does phosphatidylethanolamine offer the cell

charged head allows for interactions with negatively charged DNA

what conditions are phosphatidylethanolamine in higher concentration

conditions of cellular stress

what are the advantages of cariolipin in a cell

stabilizes the curve of the polar membrane

what conditions are concentrations of cariolipin in the cell expected to increase

shrinking cells undergoing starvation because more of the cell is in the curved region

what advantages does oleic acid offer the cel

makes the membrane more fluid due to cis bonds

what conditions are oleic acids favored in

when the membrane needs to be more fluid

what advantages do cyclopropane offer the cell

makes membrane more stiff due to planar ring

what conditions are cyclopropanes favored in

starving cells, cells undergoing acid stress, when the membrane needs ot be more stiff

what are the advantages offered to the cell by hopanoids

make the membrane more stiff by limiting motion of fatty acid side chains

when would you see the concentration of hopanoids increase

when the membrane needs be me more stiff

branched terpenoids

every fourth carbon has methyl group, causing membrane to stiffen, found in archaea

cyclopentane rings

has hydrophilic and hydrophobic regions, archaea

monolayers

archaeal membranes, super stable

what is peptidoglycan

polymer of a disaccharide linked by short amino acid chains

two types of disaccaride in peptidoglycan

NAG (G) and NAM (M)

what enzyme creates the NAG-NAM bond

transglycosylase

what enzyme crosslinks the NAM molecules between layers

transpeptidase

how does lysozyme target the cell wall

breaks the NAG-NAM disaccharide bond in peptidoglycan

how does penecillin target the cell wall

binds in the active site of transpeptidase to block it, prevents cross-linkage

how does vancomycin target the cell wall

binds to the D-ala-D-ala side chain, preventing transpeptidase from binding

what makes Gram possitive different than gram negative

has many thick layers, has teichoic acid to reinforce the layers

what makes gram negative differant from gram positive

few thin layers, has outermembrane, has periplasmic space between outer and inner membranes

inner leaflet of the outer membrane is composed of _______ which connect the outermembrane to _____

lipoproteins, peptigoglycan

what would happen if a cell failed to make lipoprotein

the OM woult not attach to the cell wall

outer leaflef of the outer membrane is composed of ______

lipopolysaccharide

what happens if piopolysaccharide is released from a lysed cell intio the body

can cause lethal endotoxic shock

where are porins located on a gram negative cell

outer membrane

four compartments for proteins in a gram negative cell

Cytoplasm

Inner Membrane (IM)

Periplasmic Space

Outer Membrane (OM)

nucleoid

area of the cytoplasm where the DNA concentrates

plasmid

small circular pieces of DNA, useful but not essential traits

Structure of PHB granules

inclusion body, intracellular phospholipid monolayer embedded with proteins

function of PHB granules

stores carbon reserves and energy (PBH)

structure of magentosomes

inclusion body, invagination of the plasma membrane

functions of magentosomes

store iron (magnetite)

help aquatic cells orient with earth's magnetic field to get the perfect amount of oxygen in a water environment

structure of endospores

membranes and protein coats around DNA

endospores function

allow cells to survive long periods without food/water in extreme conditions

vegatative cells

metabolically active form of bacteria

capsule structure

organized layer of polysaccharides outside of cell envelope

capsule functions

protect cells from detection by immune system

helps attach to surfaces

holds water

S-layer strucutre

crystalline outer layer of thick protein subunits outside of cell wall/on cell wall

S-layer function

add protective layer

may help protect cell from osmotic stress

helps cell maintain size and shape

pilus structure

straight filaments of pilin protein

pilus function

helps cells attach to surfaces

motility

aids in horizontal gene transfer by pulling two cells into contact

stalk structure

extension of the cell envelope

what structures are included in the cell envelope

outer membrane, inner membrane, cell wall

stalk function

attach to surfaces, increase surface area, secrete adhesion factors called holdfasts

flagellum structure

rotating appendages that allow bacteria to swim, made of protein monomers called falgellin

flagellum functions

movement, chemotaxis

chemotaxis

movement of bacterium in response to chemical gradients

run

flagella bundle together and push the cells forward by rotating counter-clockwise in response to attractant

tumble

flagella bundle falls apart before moving clockwise in response to a repellent

how do bacteria detect attractants

receptors

why is it called biased random walk

biased towards attractants, increasing attractant concentration increases run time

binary fission

an asexual reproduction process where a single cell divides into two genetically identical daughter cells

what role does FtsZ play in binary fission

FtsZ proteins assemble to form a Z ring that pinches the cell envelope to separate the cytoplasm of the new cells

generation time

time per generation or doubling, every generation is a doubling

batch culture

a closed-system where all nutrients are added at the beginning with no additions until the product is harvested

what is time (0) on a growth curve

the time at which the culture is inoculated

what happens during time (0) on a growth curve

the time that old cells are replaced with new

what is the lag phase on a growth cruve

no increase in number of living bacterial cells

what is happening during lag phase on a growth curve

size is increasing, damage is being repaired, environments are being sensed and their genes are being altered accordingly, cells are synthesizing ribosomes

what is log phase on a growth cruve

exponential increase in teh number of living cells

what is happening during log phase on a growth curve

cells are dividing at the max possible rate, cell metabolism is most consistent, cells are most suseptible to antibiotics

what is stationary phase on a growth curve

plateau in number of livign cells

what happens dring stationary phase on a growth curve

cells shrink so fewer nutrients are needed, new stress-resistant enzymes are synethsized, more resistance to heat and osmotic pressure, cell growth slows, sporulation

what is death phase on a growth curve

exponential decrease in the number of living cells

what happens during death phase on a growth curve

cells die due to lack of nutrients

what factors affect the duration of lag phase

growth medium of original and new culture, growth phase of inoculated cells

what factors influence the slope of log phase

quality of carbon and energy source, availabiltity of building blocks, temp, pH, O2 levels

what factors affect the max concentration of cells

oxygen, nutrient availablity

what factors affect the stationary phase

nutrient availablity

continuous culture

fresh nutrients are continuously added while equal amounts of old culture is removed to maintain expoential phase

chemostat

constantly adds nutrients and removes ewaste, can fine tune nutrients to a culture's specific needs

how does microscopic counting work

use special slide, counter number of cells in designated area and use the formula

# bacteria/mL = # counted cells/volume

advantages of microscopic counting

fast and cheap, can count all bacteria not just lab grown

Disadvantages of microscopic counting

can't distinguish between living and dead, tiny area may not represent whole

how does LIVE/DEAD staining with microscopy work

propidium iodide (red) binds DNA but cannot penetrate living cells

syto-9 (green) stains living and dead cells