cell structure

what are gram positive cells primarily composed of?

peptidoglycan

what is found in gram positive cells in abundant amounds?

teichoic acids

what do teichoic acids aid in?

• help maintain cell envelop

• protect from environmental substances

• may bind to host cells

what is found on some surfaces of peptidoglycan in gram positive bacteria?

a top layer of proteins

periplasmic space

lies between plasma membrane and cell wall and is smaller than that of a gram negative bacteria

describe the periplasmic space of gram positive bacteria in terms of protein

the space has relatively few proteins

what enzymes are secreted by gram positive bacteria?

exoenzymes

what do exoenzymes aid in?

degredation of large nutrients

describe gram negatve cell walls in terms of complexity

gram negative cell walls are more complex than gram positive

describe the layer of peptidoglycan on gram negative cells

it is a thin layer surrounded by an outer membrane

what is the outer membrane of a gram negative cell composed of?

it is composed of lipids, lipoproteins, and lipopolysaccharides

why don’t gram negative cells need teichoic acids?

they do not need teichoic acids because they have an outer membrane

what percentage of periplasmic space does the periplasmic space of gram - cell walls constitute?

20-40% of cell volume

what enzymes are present in gram negative cell walls?

• hydrolytic enzymes

• transport proteins

• other proteins

what do enzymes in gram negative cell walls lead to?

compartmentalization which leads to specialized functions

where does the outer membrane reside on a gram negative cell wall?

the outer membrane resides outside the thin peptidoglycan layer

what do Braun’s lipoproteins connet?

connect outer membrane to peptidoglycan

what three parts compose lipopolysaccharides?

• lipid A

• core polysaccharide

• O side chain (o antigen)

where is lipid A of a lipopolysaccharide embedded in?

it is embedded in the outer membrane

where do the core polysaccharide and o side chan extend from?

they extend out from the cell

what do lipopolysaccharides contribute to on the cell’s surface?

they contribute to the negative charge on the gram - cell surfaces

what is important of LPS?

• they stabilize outer membranes

• they contribute to attachment to surfaces and biofilm formation

• they create a permeability barrier

what is the function of the O antigen?

protect from host defenses

what does lipid A act as?

acts as an endotoxin

who first reported LAL and in what year?

Fred Bang in 1956

what makes gram negative cells more permeable than gram positive cells?

porin proteins and their transporter proteins

what size molecules pass through porin proteins via diffusion?

molecules ranging in sizes from 600-700 daltons

what is the reaction of gram stain attributed to?

it is attributed to the nature of cell wall

what prevents loss of crystal violet in gram +

shrinkage of the pores of peptidoglycan which causes constriction

hypotonic environments

solute concentration outside the cell is less than inside the cell

• water moves into cell, causing it to swell

• cell wall protects from lysis

hypertonic environments

solute concentration outside the cell is greater than inside

• water leaves the cell

• plasmolysis occurs

what bond do lysozymes break?

he bond between N-acetyl glucosamine and N-acetylmuramic acid

what does penicillin inhibit?

peptidoglycan synthesis

what occurs if gram positive cells are treated with lysozymes or penicillin within a hypotonic solution?

the cells will lyse

what is the term used to describe gram + bacteria that have lost their cell wall?

protoplast

what term is used to describe gram - bacteria that have lost their cell wall?

spheroplasts

what is characteristic of mycoplasma?

• they do not produce a cell wall

• plasma membrane more resistant to osmotic pressure

glycocalyx

sugar rich layer outside cell wall

• helps bacteria attach to solid surfaces

• either glycoprotein or polysaccharide

• found as capsules, slime layers, and s layers

what are capsules usually composed of?

polysaccharides

what is characteristic of capsules?

• they are well organized and not easily removed from the cell

• visibile in light microscope

what are some protective advantages of capsules?

• resistant to phagocytosis

• protect from desiccation

• exclude viruses and detergents

slime layers

• diffuse

• unorganized

• easily removed

• aid in motility

what are characteristics of endospores?

• non reproductive

• dormant

• normally initiated due to lack of nutrients

• DNA packed into a cortex

• resistant to heat and radiation

• can remain viable for at least 100,000 yrs

what acid makes endospores so resistant to heat and radiation?

dipicolinic acid, DPA

panspermia

theory that said all things have existed in some way from the beginning

s layers

regularly structured layers of protein or glycoprotein that self assemble

where do the s layers adhere to in gram - bacteria?

adhere to outer membrane

where are s layers associated to in gram + bacteria?

associated with peptidoglycan surface

in which microorganisms are s layers found?

found in al bacteria and archaea

what do s layers protect from?

protect from ion and pH fluctuations, osmotic stress, enzymes and predation

what do s layers maintain?

shape and rigidity

what do s layers promote?

promote adhesion to surfaces

what do s layers protect from?

host defenses

how do archaeal cell envelopes differ from bacterial envelopes?

differ in molecule makeup and organization

what do archaeal cells have since they lack peptidoglycan?

they have s layers to compensate

what is rare to find in archaeal cells?

capsules and slime layers

what are archaeal membranes composed of?

composed of isoprene units and ether linkages

what is typically seen in archaeal membranes?

typical to see them have a monolayer rather than a bilayer structure

what do most archaeal cells have that is external to the s layer?

most have protein sheath

if the s layer is outside the membrane, what is it separated by?

pseudomurein, similar to gram positive microorganisms

what types of bonds does pseudomurein have?

1 → 3 bonds

what type of amino acid is pseudomurein?

it is an L amino acid

pseudomurein corresponds with wich acid?

N-acetylalosaminuronic acid

what bonds does peotidoglycan have?

1 → 4 bonds

what type of amino acid is peptidoglycan?

it is a D amino acid

what acid does peptidoglycan correspond with?

N-acetylmuramic acid

what are structures of bacteria and archaea?

• cytoskeleton

• intracytoplasmic membranes

• inclusions

• ribosomes

• nucleoid and plasmids

protoplast

plasma membrane and everything within

cytoplasm

material bounded by the plasmid membrane

how many homologs of eukaryotic cytoskeletal elements have been identified in bacteria?

three have been identified

how many homologs of eukaryotic cytoskeletal elements have been identified in archaea?

two have been identified in archaea

what functions do the eukaryote homologs perform in archaea and bacteria?

roles in cell devision, protein localization, and determination of cell shape

what is FtsZ a homolog of?

tubulin

what is the function of FtsZ?

forms ring during septum formation in cell division

what is MreB a homolog of?

actin

what is the function of MreB?

maintains shape by positioning peptidoglycan synthesis machinery

what is CreS a homolog of?

intermediate filament homologues

what is the function of CreS?

induces curvature in curved rods, rare

what are intracytoplasmic membranes?

plasma membrane infoldings

in which microorganisms are intracytoplasmic membranes observes?

observed in many photosynthetic bacteria, bacteria with high respiratory activity

what are intracytoplasmic membranes analogous to?

thylakoids of chloroplasts

what is key of intracytoplasmic membranes?

they are reaction centers for ATP

where are anammoxosomes found?

in plactomycetes, they protect cytoplasm from toxic intermediates, sire of anaerobic ammonia oxidation

what is the anaerobic ammonia reaction?

NH4+ + NO2 - → N2 + 2H2O

what are inclusions?

granules of organic or inorganic material that are stockpiled by the cell for future use

how are inclusions enclosed?

some are enclosed by a single layered membrane

what are single layered membranes made up of?

proteins and some are made up of lipids

• may be referred to as microcompartments

what do storage inclusions include?

• storage of nutrients, metabolic end products, energy, and building blocks

• glycogen storage

• carbon storage (PHB)

how are microcompartments organized?

they are not bound by membranes but compartmentalized for a specific function

what are carboxysomes and what do they contain?

CO2 fixing bacteria

• contain the enzyme ribulose 1,5-bisphosphate carboxylase (rubisco) enzyme used for CO2 fixation

in what microorganisms are carboxysomes found in?

cyanobacteria

what do the inclusion, gas vacuoles, provide and where are they found?

provide buoyancy in gas vesicles

• found in aquatic, photosynthetic bacteria and archaea

where are the inclusions, magnetosomes, found, and what do they do?

found in aquatic bacteria

• magnette particles for orientation in Earth’s magnetic field, mineralized iron oxide

what does the cytoskeletal protein MamK do in magnetosomes?

helps form magnetosome chain

what do ribosomes consist of?

protein and RNA

• site of protein synthesis

how many svedburg units make up bacterial and archaeal ribosomes?

70S

how many svedburg units make up eukaryotic ribosomes?

80S

how large are the small bacterial and archaeal ribosomal RNA?

16S small subunit

how large are the bid bacterial and archaeal ribosomal RNA?

23S and 5S in large subunites

what is archaea most similar to?

more similar to eukarya than bacteria