microbio

bacteria

evolutionary separate form of life

archaea, bacteria, and eukarya

three fundamental groups of life forms termed DOMAIN

prokaryotes

unicellular organisms, nucleoid, lack of membrane-bound organelles

polysaccharide cell wall (pseudopeptidoglycan), archaeal flagella

bacteria

peptidoglycan cell wall, bacterial flagella

eukaryotes

uni/multicellular organisms, nucleus, no cell wall/ chitin wall/ cellulose wall, membrane bound organelles

evolutionary relationships

modern taxonomy classifies life based largely on WHAT using genetics and shared ancestry

0.2-2 um

bacterial cells size range

light microscope

how can bacteria be observed

cell wall

rigid outer shell, protects cell from osmotic stresses

cell membrane

lipid (hydrophobic) barrier full of proteins that contains the cytoplasm, mediates transport in and out of the cell, and scaffolds cell activity

cytoplasm

gel-like network of proteins, DNA, RNA, cytoskeletal like elements, etc., BACTERIAL NUCLEOID

nucleoid

DNA, expression machinery, DNA-binding and regulatory proteins

single circular chromosome

what does the bacterial DNA genome usually consist of

structural organization

the bacterial nucleoid has no membrane but it has a WHAT

supercoiled DNA, nuceloid-associated proteins (NAPs), origin of replication

the nucleoid consists of WHAT bound to WHAT that connect to a central point called the WHAT

FtsZ

cell diameter is maintained by what polymerization to form the Z-ring

MReB proteins

elongation of a rod-shaped cells requires WHAT

CReS (crescentin)

what is the third-shape determining protein which polymerizes along the inner curve of the crescent

endospores

found in bacteria belonging to the phylum bacillota (gram positive), extremely resistant to drying, heat, radiation, disinfectants, can remain viable for many years, serious concern for food industry, healthcare, military, tough, nom-reproductive structures that allow bacteria to survive harsh environmental conditions

aerobic rods

bacillus spp.

anaerobic cocci

clostridium spp.

bacillus species

central endospores

clostridium botulinum

terminal endospores (club shaped), gram positive, rod-shaped, anaerobic, spore-forming

neurotoxin

clostridium botulinum is a motile bacterium that produces a what

botulism

what does exposure to a neurotoxin cause

flaccid paralysis

what is botulism defined by

spastic paralysis

tetanus is defined by a

proteins

what orders the bacterial chromosome into the nucleoid?

cytoskeletal elements

organize and coordinate cell processes

the inner membrane

for gram positive or diderm bacteria, the cell membrane is often called what

cytoplasmic contents from leaking out

what does the cell membrane prevent

a hydrophobic barrier against the passage of many compounds

what does the cell membrane form

glycerol with ester links to each of two fatty acids and a phosphoryl polar head group

what do phospholipids consist of

bilayer of lipids

what do bacterial membranes consist of that face each other tail to tail?

water, gases, small unchanged molecules

what can pass through membrane

membrane is more rigid and resists increasing temperature

what happens when saturated fatty acids pack tightly or stick to each other

sacculus

what is the bacterial cell wall also known as

peptidoglycan (PG)

what is cell membrane made of

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

long chains of PG consist of repeating units of a disaccharide composed of what

mycoplasma pneumoniae

among the smallest free-living bacteria, genome is small, associated with respiratory infections “walking pneumonia”

lacks a cell wall (no peptidoglycan), inherently resistant to beta-lactam class of antibiotics

IMPORTANT FACT ABOUT mycoplasma pneumoniae

gram positive

relatively simple, thick layer of PG, teichoic acids, no outer membrane, no LPS

gram negative

relatively complex, thin layer of PG, no wall teichoic acids, outer membrane, LPS present

crystal violet

gram positive stain (monoderm)

endotoxin

LPS also known as

outer (O) antigen

A repeating pattern of highly variable sugars

core

Highly conserved in all gram negative bacteria, forms a barrier against detergents

lipid A

Anchors LPS to outer membrane. Very hydrophobic!

outer membrane

diffusion barrier, protects against chemical assault BUT also prevents nutrient acquisition

porins

form channels in outer membrane to allow facilitated diffusion of small hydrophilic molecules into the periplasm

bacteria with atypical cell walls

when is gram staining not used

mycoplasma species, mycobacterium tuberculosis

two examples that do NOT stain

flagella

helical propellers that drive the cell forward like the motor of a boat

pilus or fimbria

a hair- like cell-surface appendage found on many bacteria and archaea

sex pilus

Specialized types of pili can transfer DNA between two bacterial cells

antimicrobial compound

a broad umbrella term for agents fighting microbes (bacteria, viruses, fungi, parasites)

antibiotics

specifically target bacteria

selective toxicity

what do antibiotics exhibit, magic bullet concept

magic bullet

in 1904 Paul Erlich proposed that a successful antimicrobial compound should be a WHAT that selectively kills or inhibits the pathogen but not the host

key aspects of a microbe’s physiology are different from those of eukaryotes

why is selective toxicity possible

bactericidal

Kill bacteria

• Used when host

defense mechanisms

are impaired

• Required in

endocarditis,

meningitis, kidney

infection, etc.

bacteriostatic

Inhibit bacterial

growth

• Used when host

defense

mechanisms are

intact

• Used in many

types of infections

preventing the cross-linkage of NAM subunits

most antibiotics inhibit PG synthesis by

growing

inhibition of cell wall synthesis are effective only when bacterial cells are WHAT

penicillin family, cephalosporins

antibiotics in the beta-lactam group

penicillin

an antibiotic formed from the condensation of cysteine and valine, Effective primarily against gram positive bacteria

Ampicillin and Amoxicillin

Effective against gram positive AND some gram negative bacteria

• Largely ineffective against most clinical strains of Staphylococcus aureus

Cephalosporins

contains a 6-membered dihydrothiazine ring fused to the beta-lactam ring

• Depending on generation, active against gram positive AND gram negative bacteria

monobactams

In Monobactams the beta-lactam ring is not fused to another ring

• Narrow spectrum  Pseudomonas aeruginosa

cross bridges

Transpeptidases bind to terminal D-Ala- D-Ala dipeptides and catalyze the formation of

inactivate

Beta-Lactams bind to and WHAT transpeptidases to prevent PG synthesis

penicillin binding proteins (PBPs)

Transpeptidases are also referred to as

vancomycin

works by by binding to the Dalanyl- Dalanine ( DAla-DAla) termini of peptidoglycan precursors  this blocks the PBPs that build and cross-link the cell wall

folic acid

is crucial for purine synthesis, acting as a coenzyme (tetrahydrofolate) needed to build the purine ring (like adenine and guanine) in the de novo pathway

sulfa drugs

compete with para-aminobenzoic acid (PABA) for binding to Dihydropteroate Synthase (DHPS)  blocks folate synthesis

trimethoprim

binds to and inhibits dihydrofolate reductase  blocks folate synthesis, can be combined with sulfa drugs to inhibit different steps in folate synthesis

bactrim, cotrim, septa

Trimethoprim/Sulfamethoxazole (TMP/SMX) brand names

negatively supercoiled

The nucleoids of bacteria are kept

DNA gyrase

Negative supercoiling of bacterial DNA is catalyzed by Type II topoisomerases such as

fluoroquinolones

inhibit bacterial DNA Gyrase with little/no effect on eukaryotic versions

rifampin

(also called rifampicin) binds to and inhibits bacterial RNA polymerase preventing transcription, one of two primary drugs used in the treatment of pulmonary tuberculosis and leprosy, bactericidal

translation

is the process by which proteins are synthesized using RNA molecules as a template, catalyzed by ribosomes

aminoglycosides

display bactericidal activity against “most gram-negative bacilli”

• Common examples: Gentamycin, Tobramycin, Amikacin

aureomycin

derived from a soil sample taken from Sanborn Field

tetracyclines

are bacteriostatic rather than bactericidal, are used in the treatment of infections of the urinary tract, respiratory tract, the intestines and acne vulgaris

doxycycline

is first-line treatment for both Rocky mountain Spotted Fever (RMSF) and Lyme disease

macrolides

Effective against gram positive and some gram negative bacteria; effective against Mycoplasma pneumoniae

chloramphenicol

Broad spectrum of activity

• Crosses blood-brain barrier  useful in infections of the central nervous system

clindamycin

is used for the treatment of a number of bacterial infections, including osteomyelitis (bone) or joint infections, pelvic inflammatory disease, endocarditis and Toxic Shock Syndrome

antimicrobial resistance (AMR)

is an urgent global public health threat

microbe (mostly prokaryotes)

living organism that is only visible by using a microscope

spontaneous generation

living creatures could arise from nonliving matter and that such processes were comomonplace and regular

louis pasteur

who’s experiments show that microbes do not generate spontaneously

disease transmission

what did koch demonstrate the principle of or the chain of infection

bacillus anthracis

agent of anthrax

observe, isolate, inoculate, recover

4 steps of koch’s postulates

mycobacterium leprae (leprosy), all viral agents

what pathogens cannot be grown in pure culture

germ theory

infectious diseases are caused by specific kinds of microbes

mutualism

both species benefit from the association