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external structures on bacteria

capsules, flagella, and pili



layers of organic polymers attached to the exterior of bacteria that for hydrophilic gels surrounding the cells of some bacteria

usually polysaccharides except in Bacillus anthracis, which ahs a poly-D-glutamic acid capsule

capsules prevent dessiccation in the environment

crucial role in the virulence of certain pathogens

prevents phagocytosis by preventing complement activation on the cell surface


human pathogens in which a capsule is considered to be an important virulence determinant

Streptococcus pneumoniae

Neisseria meningitidis

Haemophilus influenzae

Klebsiella pneumoniae

Streptococcus agalactiae

some E. Coli


K antigen

capsules of certain bacteria used for serological typing


what two types of disease do encapsulated bacteria primarily cause?

meningitis and bacteremia in individuals without functional spleens



long, helical filaments

hollow and rigid

composed of a single protein, flagellin

flagellin passes through the hollow filament and self-assembles at the tipck

flexible hook connects the flagellum to a basal body in the bacterial envelope

basal body is the motor

responsible for bacterial motility


H antigens

flagella that can be used to serologically distinguish and classify certain bacteria


flagella and movement

rotate up to 40-60 revolutions/second

energy is from the flow of protins into the cell

as fast as 100 cell lengths/second




the ability to move toward attractants and away form repellents


toll-like receptor-5 (TLR-5)

recognize the presence of flagella through binding

leads to an inflammatory response


pili (fimbriae)

long, thin filamentous structures distributed over the surface of some bacteria

made up of pilin and sometimes minor proteins

mediate adherence, bind receptors that consists of sugar residues on glycolipids or glycoproteins int he host cell membrane

twitching motility

biofilm formation


phase variation

the ability to turn production of particular surface proteins, such as flagellin or pili, on and off

leads to antigenic variation because the changing of these surface proteins deceives the host immune system


bacterial cytoplasm

site of synthetic reactions, many ribosomes

mostly proteins and RNA


bacterial ribosomes

70S ribonucleoproteins tructures composed of 50S and 30S subunits

the 50S subunit has 2 RNA molecules and 34 proteins

the 30S subunit had one RNA molecule and 21 proteins


bacterial chromosome

a single circular molecule, known as the nucleoid

E. Coli chromosome is 1 mm long with 4.6 megabases

chromosome is very tightly packed within the bacterium

contains circular molecules called palsmids, which often contain drug resistant genes

chromosome replicate by DNA polymerase, starting at the oriC

daughter chromosomes are initially linked but are separated by DNA gyrase


transcription and translation

genes on the chromosome are transcribed by RNA polymerase

genes can be organized into operons

first amino acid is a formyl-methionine

multiple ribosomes may translate a single mRNA simultaneously

translation and transcription are linked


identification of nonculturable bacteria

16S rRNA PCR amplification

broad-range PCR primers

sequencing the amplified region

infer the phylogeny of the unknown organism

ex. bacillary angiomatosis (Bartonella henselae)

ex. Whipple's disease (Tropheryma whippelii)


WQhipple's DIsease



weight loss


rarely heart or CNS involvement

can't culture bacteria that causes this disease


bacterial spores

highly resistant, metabolically inactive dormant forms of bacteria

developed within the vegetative cells

promote survival under environmentally unfavorable conditions

resistant to heat, UV irradiation, drying, and chemical agents

favorable conditions -> spores germinate and form vegetative cells

only some gram-positive bacilli (Clostridium and Bacillus)




some Gram-positive bacilli are able to form these tructures that deveop within vegetative (dividing) cells



O-side chains


bacterial metabolism

10 to 100 times faster than the cells in our bodies

must obtain nutrients from the environment such as iron

developed ways of stealing it from human hosts



low molecular weight molecules secreted by bacterial cells that removes iron from host molecules and allow bacterial cells to take it up

other bacteria produce surface receptors to which lactoferrin and transferrin can bind, donating its iron



organic compounds serve as electron donor sand acceptors

energy is generated by substrate-level phosphorylation

ineffiicent generation of energy

does not require oxygen



the electron acceptor is O2 for aerobic respiration or nitrate (or some othe rinorganic compound) for anaerobic respiration

electrons are transported through carriers

produces relatively large amounts of energy


respiration - ETC

sequence of carrier molecules that are capable of oxidation and reduction

electrons pass through the chain

energy is released

drives chemiosmosis

pushed to final electron acceptor

results in the majority of ATP production


oxidase test

measures the ability of bacteria to oxidize and therefore change the color of N,N-dimethyl-p-phenylenediamine

bacteria that contain cytochrome c are "oxidase positive"



electron transport

protons pumped from the cytosol to the external side of the cytoplasmic membrane

protonmotive force generates energy gradient to make ATP from ADP

powers flagellar rotation and uptake of some small molecules into the cell


metabolism as an identification tool

oxidase test

identification based on the sugars and other molecules they can use as a fuel source


bacterial utilization of oxygen

different bacteria may use oxygen as part of energy generation and respiration

some are unable to use oxygen and are killed by its deleterious effects

two toxic products are hydrogen peroxide and superoxid anion