Microbio Exam 2

the cell

the fundamental unit of any living organism- exhibits the basic characteristics of life

cell morphology

the shape of cells

bacilli

rod shaped

cocci

spherical cells 

vibrio

comma shaped

stella

star shaped

coccobacilli

ovoid 

spirochetes

spiral shaped, corkscrew motion

arrangements

a result of their cell division patterns

diplo-

pairs

strepto-

chains

staphylo-

grapelike structures

palisade

clusters of bacilli

prokaryotic reproduction

binary fission

**eexception of binary fission

Epulopiscium 

give birth to live off spring

giant bacteria (200-700um)

cigar shaped

lives inside surgeonfish

hyphae

branching filaments of cells

trichomes

smooth unbranched chain of cells

cell envelope 

plasma membrane and cell wall

outside of cell wall

outermost layer in the cell envelope

glycocalyx - capsules and slime layers, aid in attachment to solid surfaces, biofilms

prokaryotic glycocalyx

sugar coat

slimy or sticky

carb rich material secreted outside the cell wall - polysaccharide and polypeptide

glycolax- capsule

highly organized and firmly connected 

allows bacteria to evade the immune system 

Klebsiella pneumoniae

Neisseria meningitidis

Streptococcus pneumoniae 

glycocalyx- slime layer 

loosely connected to the cell wall - contains glycoproteins 

aids in protecting the cell from dehydration and nutrient loss 

Pseudomonas spp. 

extracellular polymeric substance (EPS)

helps cells form biofilms

part of glycocalyx

protects cells within it, aides communication and attachment to surfaces

s-layer

proteinaceous coat covering the entire surface

adhesion and biofilm formation

interact with immune cells

protect from ion and pH fluctuations and osmotic stress

flagella 

long filamentous appendages 

propel bacteria 

protein - flagellin

peritrichous

flagella covers the whole cell

polar

flagella at one or both poles

monotrichous

single flagellum at one end

lophotrichous

a lot of flagella coming from one pole

amphitrichous 

flagella from both poles of the cell 

parts of the flagella

filament, hook, basal body

flagella filament

outermost region

flagella hook

attaches to the filament 

flagella basal body 

consists of rod and pairs of rings

anchors flagellum to the cell wall and membrane 

periplasmic flagella

located in the space between the plasma membrane and the cell wall

allow spirochetes to move in corkscrew motion

proximal structure of flagella

gram-pos: 2 rings

gram-neg: 4 rings

run and tumble system 

allows the cell to sense its environment and change direction 

run - bundle together and swim in straight line (counterclockwise)

tumble- cant form bundles (clockwise)

chemotaxis

movement in response to chemical stimulus

phototaxis

movement in response to light

aerotaxis 

movement in response to oxygen levels 

proton motive force

“energy” to turn

movement of protons down a concentration

translocate ions from the periplasm to the cytoplasm

generate torque

polymerization of actin

propulsion of bacteria into adjacent cells

Shigella dysenteriae

Listeria monocytogenes

gliding motility “slime trails”

smooth sliding over a surface 

Myxobacteria 

Cyanobacteria 

twitching motility

slow pili - gripping, pulling, releasing

N. meningitidis

P. aeruginosa

pili

only one or two per cell

involved in DNA transfer

used to connect bacteria to allow the transfer of DNA from one cell to another - conjugation or sex pili

twitching or gliding motility

fimbriae 

shorter than a pili

occur at poles or are distributed over the entire surface 

adhere to surfaces or to each other 

involved in biofilms 

bacteria adhere to epithelial surfaces 

cell wall

shape of the cell

prevent osmotic lysing

site of action for some antibiotics

cell wall structure

peptidoglycan core component

polysaccharide- peptide matrix

peptidoglycan structure (murein)

repeating disaccharides attached by polypeptides 

N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)

linked in rows 10-65 sugars to form carb backbone 

adjacent rows are linked by polypeptides - cross-linked NAM and peptide chain 

amino acids and cross-linking vary 

d-form amino acids

associated with NAM

add more resilience and less susceptible to enzyme degradation

peptidoglycan secretion

1. NAM is synthesized in the cytoplasm

2. NAM linked to bactoprenol

3. NAG added to NAM

4. Bactoprenol flips NAM-NAG to the periplasm

5. add NAM and NAG to chain 

6. transpeptidase- catalyzes cross-linking 

site of attack - lysozyme 

lysozyme cleaves the backbone of peptidoglycan- hydrolyzes the glycosidic bond 

occurs naturally in eukaryotic cells - sweat, tears, mucus, saliva 

1. lysozyme cuts peptidoglycan

2. without an intact cell wall, the rod shape is lost 

3. in hypotonic conditions → water rushes in 

4. internal pressure causes cell lysis

site of attack - lysostaphin

acts on the crossbridge of certain Staphylococcus species only 

site of attack- transpeptidase

beta-lactam drugs inhibit new cross-links

NAG and NAM continue to be added → growth → cell bursts

vancomycin

non beta-lactam cell wall synthesis inhibitor

prevent peptide side chains

mechanism for antibiotic resistance

beta-lactamases - hydrolyze the C-N bond of the beta-lactam ring and destroy the activity of these antibiotics

Gram-positive cell envelope

thick outer layer of peptidoglycan 

very narrow periplasmic space 

teichoic acids in the peptidoglycan 

lipoteichoic acids in peptidoglycan and plasma membrane

Gram-negative cell envelope

varying width periplasmic space 

very thin layer of peptidoglycan 

outer membrane composed of lipopolysaccharide (LPS)

lipopolysaccharide (LPS)

1. lipid A - base

2. core polysaccharide

3. O-antigen - side chain at end of LPS

exotoxin

toxic substances released outside the cell

proteins produced inside pathogenic bacteria are part of their growth and metabolism

most commonly gram-pos

secreted during log phase

endotoxins 

toxins composed of lipids that are part of the cell membrane 

lipid portions of LPS of Gram-negative bacteria (lipid A)

released when bacteria die and the cell wall breaks apart 

gram-positive cell wall

peptidoglycan layer with large pores in its matrix

gram-negative cell wall

porin and TonB proteins in its outer membrane to transfer molecules into the periplasmic space

Mycoplasma

smallest known bacteria

pass through bacterial filters- mistaken for viruses 

have sterols (make membrane more flexible) → protect from lysis 

acid-fast cell walls

Mycobacterium

high concentrations of hydrophobic waxy lipid - mycolic acid

carbolfuchsin penetrates

waxy layer prevents large uptake of nutrients → acid-fast growth very slow

plasma membrane

phospholipids and proteins

selective barrier

thin

flexible

transport of molecules 

where is ATP made in prokaryotic cells?

in plasma membrane 

passive diffusion

high conc. → low conc.

not energy dependent

rate of diffusion determined by concentration gradient

H2O, O2, and CO2

facilitated diffusion

combines with a transporter protein in the membrane

not energy dependent

high conc. → low conc.

active transport 

energy-dependent 

against gradient 

specific carrier proteins 

primary active transporters (ABC transporters)

use energy provided by ATP hydrolysis

secondary active transporters (MFS transporters)

couple the potential energy of ion gradients

symport and antiport

siderophores 

molecules that chelate iron 

1. siderophore binding - iron loaded to iron free 

2. iron exchange 

3. conformational change 

4. iron-siderophore translocation 

destruction of plasma membrane

target of antimicrobial agents

70% ethanol

disinfectants/detergents

cause leakagea of intracellular contents → cell death

cytosol

substance in plasma membrane

80% water

proteins, carbs, lipids, ions, low MW compounds

thick, semitransparent, elastic

protein filaments responsible for shape

bacterial cytoskeleton 

series of internal proteins 

keep everything in the cell and move things to the right locations 

tubulin-like and actin-like

tubulin homologs

FtsZ - cell division

BtubA/BtubB - unknown

actin homologs

FtsA- cell division

MamK- positioning magnetosomes

MreB/Mbl - cell division

intermediate filament homolog

CreS (cescentin) - induces curvature in curved rods 

unique bacterial cytoskeletal proteins

MinD - prevents polymerization of FtsZ at cell poles

ParA (chromosome encoded form)- segregates chromosomes

MreB

maintains cell shape, segregates chromosomes, localizes proteins

cell wall synthesis during cell division - provides structure

MreB polymerizes to form actin-like helical bands next to plasma membrane

FtsZ

cell division - makes Z-ring at site of cell division

the mucleoid

contains a single long, continuous, circular DNA → bacterial chromosome

no nuclear envelope

all info for structure and function

also contain plasmids

plasmids

not connected to the mail bacterial cell

circular double-stranded pieces of DNA

5-100 genes not crucial for survival

gained/lost without harming the cell

toxins, antibiotic resistance, tolerance to metals

ribosomes

function as sites of protein synthesis

high # of ribosomes → growth

Svedberg- unit of relative rate during centrifugation

antibiotics work on inhibiting protein synthesis

70S ribosomes 

prokaryotic cells 

50s subunit- erythromycin and chloramphenicol antibiotics target 

30s subunit- streptomycin and gentamicin antibiotics target 

80S ribosome

eukaryotic ribosome

inclusions

reserve deposits

metachromatic granules (volutin) 

phosphate reserves 

polysaccharide granules

energy reserves

lipid inclusions 

energy reserves 

sulfur granules

energy reserves

carboxysomes

enzyme for fixation during photosynthesis

gas vacuoles

protein-covered cylinders that maintain buoyancy

magnetosomes 

iron oxide inclusions 

act like magnets- protect cells against hydrogen peroxide accumulation 

endospores

metabolically inactive structures that allow certain cells to enter a dormant state

highly resistant to environmental stresses - used to survive harsh conditions

sporulation

1. The spore septum isolates new DNA and a small section of cytoplasm

2. The membrane surrounds DNA

3. spore septum surrounds isolated portion - forespore w/ two membranes

4. peptidoglycan layer forms between membranes

5. spore coat forms

6. endospore is freed from cell

endospores in the Gram Positive Bacillius and Clostridium

Clostridium tetani - tetanus 

Clostridium botulinum - botulism

Clostridium perfringens - gas gangrene

Clostridium difficile - severe diarrhea

Bacillus anthracis - anthrax

Coxiella burnetii

Gram-negative

Q-fever - mild flu-like symptoms

Cliostridium botulinum

gram-positive

obligate anaerobes

bacillus

produce heat-resistant endospores

ferments sugars and amino acids

found in soil, lake sediments, and decaying vegetation

botulism