Chapter 3: Classification of Microbes: Bacterial cell types and structures

Bacteria Size

0.2 to 2.0 um diameter and 2 to 8 um long

Bacteria shape

coccus, bacillus, spiralor

Arrangement of bacteria

cell division planes bacterial cell arrangements

Glycocalyx

coat/layer surrounding the bacterial cell

made up of polysaccharide or polypeptide

2 types of glycocalyx

capsule and slime layer

What is virulence

degree to which a pathogen causes diseases

What is virulence factor?

component of an organism that determines its capacity to cause disease

Capsule function

protects cell from phagocytosis, attachment to tissue, food source

Slime layer function

trap nutrients, prevent dessication

Flagella

long appendages for mobility

Motility of flagella

50 um/sec = 0.0001 mph = 37 cell lengths/sec

rotates like a propellor

propels bacteria through series of “runs” and “tumbles”

Flagella Structures

Filament, hook, basal bodyF

Flagella filament

flagellin protein and hollow core

Flagella Hook

attachment of filament to the motor

Flagella basal body

anchor and motor

Monotrichous

single flagellum

Amphitrichous

tuft of flagella at each pole

Lophotricous

tuft of flagella from one pole

Peritrichous

flagellum over the whole surface

Flagellin protein

antigen

H Ag

FlagellaO

O Ag

LPS

K Ag

capsule

Taxis

movement of bacteria in response to stimuli (attractant or repellent)

Chemotaxis

chemical stimuli

Phototaxis

light stimuli

Axial filament

internal flagella

Fimbriae and Pili

short hair-like appendages used for attachment or conjugation (gram negative bacteria only)

Fimbriae

Polar position or over whole surface

few to 100 per cell

Pili

Longer than fimbriae, 1 or 2 per cell