MFM II - Bacterial Classification & Structure

traditional classification looks at what?

• gram staining

• colony and cell morphology and arrangement

• growth conditions (temperature, fermentation, respiration, aerobic vs anaerobic)

• biochemical reactions

nucleic acid homology classification is based on what?

• relatedness of DNA

• G+C content

• DNA hybridizations

• phenotypic traits not considered

what describes general properties of bacteria?

• nucleoid - not membrane bound → single circular ds DNA chromosome

• no membrane bound organelles

• rigid cell wall

• 70s ribosomes

• electron transport chain takes place in cytoplasmic membrane

• polycistronic messages

• no introns involved in transcription

Prokaryotic cells have what kind of DNA?

circular DNA

Prokaryotic cells have what kind of ribosomes?

70s

colony morphology involves what parameters?

size, shape, constancy, pigment, odor

what is virulence?

the relative capacity of a pathogen to overcome body defenses

what are virulence factors?

components of pathogens that allow the organism to increase its ability to induce disease/infection

what describes virulence factors?

• may be spread through populations via mobile genetic elements

• may be structural component, enzymes, toxins released from the cells

what are functions of the capsule/slime layer?

• protect cell from environment

• protect cell from uptake by phagocytes

• attachment

the capsule/slime layer can be made up of what?

• polysaccharides

• peptidoglycan

• proteins

• glycoproteins

• lipids

biofilms are important sources of what?

infection

biofilms can form on what?

• form on or within indwelling devices

• on living tissues like the teeth

what have been identified as components of biofilms?

bacteria and yeasts

biofilms attach tenaciously to surfaces and in most cases the binding is what?

irreversible

biofilm can have what effects?

• increase spread of infection

• bacteria are protected from immune attack and antibiotic treatment

studies have shown that antimicrobial resistance is effective spread through what?

biofilm populations

duration of indwelling device correlates with what?

biofilm infection risk

• bottom line get the device out as quickly as possible

pili or fimbriae is only found on what?

gram negative bacteria (except streptococcus)

somatic pili facilitates what?

adhesion (virulence factor)

what describes sex pili?

• longer - used in conjugation

• male cells with conjugal plasmid

what is the function of flagella?

chemotaxis (motility)

• counter-clockwise = swimming

• clockwise = twiddle

what are components of flagella?

• H antigen

• basal body

• hook filament (they rotate - do not beat)

what is responsible for the cell shape and structural rigidity of the prokaryotic cell wall?

peptidoglycan

peptidoglycan is made of what and how?

NAG and NAM

• crosslinked by tetrapeptide bridge: attached to NAM

what are features of gram positive cell structure?

• thick peptidoglycan

• lipoteichoic acid

• teichoic acids

what are features of gram negative cell structure?

• surface protein layer

• outer membrane (OM)

• periplasmic space (peptidoglycan found within this space)

• peptidoglycan (thinner, less cross-linked)

• cytoplasmic (inner membrane)

what is the composition of the outer membrane of gram negative cell structures?

• lipopolysaccharides (LPS)

• phospholipids

• proteins

regarding LPS structure, what describes lipid A?

• heat stable toxin

• activates macrophages and complement

• mitogenic for B cells

• induces interferon production

• causes tissue necrosis

• adjuvant properties

LPS structure involves what?

• lipid a - heat stable toxin

• CORE - short series of sugars

• O-antigen - dispensable

regarding LPS structure, what describes O-antigen?

• hydrophilic

• major serologic determinant

• virulence factor

the periplasmic space of gram negative bacteria contains what?

• binding proteins

• degradative enzymes

• detoxifying enzymes

• peptidoglycan cell wall

• Braun’s lipoprotein

what describes the structure of the cytoplasmic membrane?

composed of phospholipids (30%), proteins (70%), and small amount of carbohydrates

what describes the function of cytoplasmic membrane?

• enzymatic activity

  • electron transport

  • oxidative phosporylation

  • synthesis of of peptidoglycan

  • transport and chemotactic systems

  • bound ribosomes

• osmotic barrier

  • simple and facilitated diffusion

  • active transport (PTS)

what describes endospores?

• resistance to killing (heat, freezing, drying, chemicals, radiation)

• cryptobiotic (no metabolic activity)

• means of survival (not reproduction)

endospores are means of what?

survival (not reproduction)

what are structures of endospores?

• core

• spore wall

• cortex

• spore coat

• exosporium

the core of an endospore contains what?

• genome

• machinery for protein synthesis

• enzymes for energy generation and AA biosynthesis

• no RNA or free amino acids

what describes the spore wall of endospores?

• peptidoglycan like vegetative cell

• forms new cell wall upon germination

what describes the cortex of endospores?

• novel peptidoglycan

• thickest layer - concentric rings - provides strength

what describes the spore coat of endospores?

• thick layer of keratin-like protein

• many disulfide bonds between proteins

• impervious - responsible chemical and radiation resistance

what describes the exosporium of endospores?

• non-essential

• maybe remnants of membrane

• frequently missing

spore germination activation can be what?

spontaneous

spore germination can be activated due to what?

• heat

• aging

• low pH

• chemical treatment

what describes the phases of germination?

• cortex swells

• hydrolysis begins

• H20 uptake

• loss of heat resistance

• excretion of Ca and dipicolinic acid

in regards to spore germination, what describes outgrowth?

• core enlarges

• mRNA synthesis

• protein synthesis

• energy is by simple glycolysis

• spore wall thickens

• spore coat ruptures

• new cell emerges