Introduction to Bacteriology

bacteria structure

single celled

0.2-2.0 um in diameter

2-8 um in length

there are __x _ bacterial cells than human cells

10, more

Antonie van Leeuwenhoek

created glass lenses and engineered a microscope with ~270x magnification

Hans Christian Joachim Gram

developed gram staining technique (1884)

noticed that some bacteria retained color and some became de-colorized by alcohol.

a

bacillus (rod)

b

coccus

c

spirillus

tetrad shape on slide

grape-like cluster on slide

common cocci that clumps in tetrads and grape like clusters

staphylococcus species

staphylococcus and streptococcus species are gram _

+

streptococcus species forms

chains

chain formation on bacterial slides

diplococci structure on slide

bacillus, listeria, lactobacillus species are all

gram + bacilli

neisseria and moraxella species are both

gram - cocci

E. Coli, K. Pneumoniae, Proteus mirabilis, P. aeruginosa are examples of

gram - bacilli

vibrio and campylobacter species are examples of

gram - curved bacilli

Glycocalyx

substances surrounding cells

consists of capsule and slime layer

bacterial glycocalyx structure

sticky, gelatinous material composed of polysaccharides

capsule structure

organized and firmly attached to the cell.

slime layer structure

unorganized and loosely attached to the cell

capsule functions

protects bacteria from phagocytosis

protects bacteria from drying out

may provide a food source

used to diagnose infection due to the variations in sugars

capsule in slides

capsule in petri dish

slime layer functions

protects cells within

facilitates communication

enables cells to survive by attaching to various surfaces in environment

atrichous flagella

lack flagella

polar flagella

single one at one end (monotrichous)

at both ends (amphitrichous)

tuft of at one end (lophotrichous)

peritrichous flagella

distributed over entire cell

flagellar protein is also called _____ and can be used to __

H antigen; identify variations within species

a

monotrichous

B

lophotrichous

C

Amphitrichous

D

Peritrichous

fimbriae

can occur at poles or over entire surface of bacteria

can be a few or several hundred

fimbriae function in bacteria

allow bacteria to adhere to each other

allow bacteria to adhere to epithelial surfaces in humans

bacterial pathogens that cause pharyngitis, urinary tract infections, and sexually transmitted diseases often have ___.

fimbriae

Pili structure

longer than fimbriae, only 1 or 2 per cell

pili structure

motility (twitching)

dna transfer (conjunction)

bacterial conjugation allow for

exchange of DNA that can add a new function to the recipient of the cell (ie. antibiotic resistance)

Cell wall structure

complex, semi-rigid, composed of peptidoglycan

cell wall functions

prevents bacterial cell from rupturing under osmotic pressure

helps maintain shape of bacterial cell

gram positive bacteria have ___ peptidoglycan

thick

gram negative bacteria have ___ peptidoglycan and

thin, porin channels, lipoprotein membrane, LPS

Lipopolysaccharide (LPS)

includes O polysaccharide and Lipid A

the first line in the LPS example is the

o polysaccharide

the second line in the LPS example is the

lipid a

outer membrane structure in gram negative cell wall

lipid bilayer containing polysaccharides and proteins

outer membrane function in gram - cell well

anti-phagocytic

barrier to substances that are detrimental to cell

provides selective passage via porin channels.

A

Cell wall

B

peptidoglycan layer

c

porin with channel

d

o polysaccharide

e

lipid a

f

lipopolysaccharide (LPS)

g

outer membrane

h

phospholipid

I

protein

lipid a (endotoxin)

responsible for symptoms associated with gram - infections; ex. fever, dilation of bv, shock, blood clotting)

O polysaccharide

extends outward from lipid a and functions as an antigen

A

liptoeichoic acid

b

cell wall

c

plasma membrane

d

peptidoglycan layers

lipoteichoic acid

not present in gram - bacteria

may aid in attachment to mammalian cells

can cause endotoxin-like response

Gram + cell wall additional components

c-carbohydrates

protein a

m protein

c carbohydrates

allows for differentiation of some bacteria (ie streptococci)

protein a

antiphagocytic

can be used for identification

m protein

antiphagocytic

can be used for identification

L forms

created when bacteria are exposed to lysozyme or antibiotics

will live and divide repeatedly or return to walled state

mycoplasma has ____ cell wall

no

plasma membrane

in both gram pos and neg cells

serves as selective barrier

plasma membrane structure

enzymes that build peptidoglycan

structural support

channels that allow for selective entry/exit

bacterial cytoplasm

thick and aqueous

contains carbohydrates, enzymes, lipids, inorganic ions and low mw compounds.

structures inside bacterial cytoplasm

nucleoid

ribosomes

endospores

nucleoid

contains 1 long, circular thread of dsDNA

100x longer than bacterial cell

supercoils

plasmid

small, circular dsDNA molecules that are extrachromosomal

not crucial for survivial

can carry genes acquired from other bacteria

vertical transfer of genetic material

replication

horizontal transfer of genetic material

transformation or conjugation

transformation

conjugation

horizontal transfer of genetic information by transduction

dna is transferred from donor cell to recipient cell inside virus that infects bacteria (bacteriophage)

inside human intestinal tract bacterial dna transfer is

horizontal

bacterial ribosomes are __S and human ribosomes are _S

70;80

endospores

formed when essential nutrients are depleted

formed by gram + bacteria

can survive extreme heat, lack of water, exposure to toxic chemicals and radiation

steps of endospore formation

1. dna in cell replicates

2. double layer of cell membrane forms around dna

3. membranes encircle dna

4. peptidoglycan layer forms between 2 membranes

5. thick protein coat forms

6. endospore is released