Cell Biology of Bacteria
BACTERIAL FACTS
Scientists have named and described more than 4,000 species of bacteria
New ones are discovered so rapidly, however, they estimate the number of unknown
species in the millions
Almost every time scientists search among bacteria in a soil or water sample, they
discover previously unknown species
The overwhelming majority of bacteria are harmless to humans or animals
Bacteria get virus infections
Antibiotics and other bacteria-derived materials are the basis of a $50 billion annual
market for biotechnology products
Oil spills are cleaned primarily by bacteria that feed on oil
About 10 percent of human body weight and 50 percent of the content of the human
colon is made up of bacteria (Escherichia coli)
each square centimeter of human skin hosts an average of 100,000 bacteria
Washing removes many, but they reproduce so quickly--doubling every 20 minutes-that the population is restored in hours
So many bacteria live underground that their total weight has been estimated at 100
trillion tons
If these microbes were spread over Earth's land surface, they would make a layer
five feet thick
CLASSIFICATION
Microbes
organisms smaller than the eye can detect
bacteria
fungi
protists
virus
CELL TYPES
Prokaryotes
Eukaryotes
Viruses
PROKARYOTES
Monera
bacteria
1 micron diameter
EUKARYOTES
algae, protozoa and fungi
5 - 100 microns
VIRUSES
neither prokaryotes nor eukaryotes
informational parasites
each kingdom has its own associated viruses
MICROBIOLOGY
disease
agriculture
food and drink
chemical products
basic research
biotechnology
BACTERIA SHAPE
range in size from 0.20 to 2.0 micrometers in diameter
1) Bacillus
2) Spiral
3) Cocci
BACILLUS
Rod shape
Diplobacilli
Two bacilli together
Streptobacilli
Chains of bacilli
Vibrios
curved rods
SPIRAL
spirillia
Spiral, helical, corkscrew shape that is rigid
spirochete
the organism is flexible and undulating
COCCI
spherical shaped
diplococci
remain in pairs
streptococci
chains
staphylococci
clusters
Moraxella catarrhallis
inhabitant of the upper respiratory tract, especially the nasal cavity
notice some are in the diploid state
CELL MEMBRANE
phospholipid bilayer
integral and peripheral proteins embedded
maintains the selective permeability of the cell
has respiratory enzymes
CELL WALL
cell wall surrounds the cell membrane
Structurally, the wall is necessary for
1) maintain shape
2) counter osmotic pressures
3) attachment sites for bacteriophages
4) platform for surface appendages
CELL WALL
1) Maintaining the cell's characteristic shape
the rigid wall compensates for the flexibility of the phospholipid membrane
and keeps the cell from assuming a spherical shape
2) Countering the effects of osmotic pressure
the strength of the wall is responsible for keeping the cell from bursting when
the intracellular osmolarity is much greater than the extracellular osmolarity
3) Providing attachment sites for bacteriophages
teichoic acids attached to the outer surface of the wall are like landing pads
for viruses that infect bacteria
4) Providing a rigid platform for surface appendages
flagella, fimbriae, and pili all emanate from the wall and extend beyond it
CELL WALL
cell walls of all bacteria are not identical
cell wall composition is one of the most important factors in bacterial species
analysis and differentiation
clinically contributes to ability to cause disease
site of action of antibiotics
There are two major types of walls:
Gram-positive
Gram-negative
GRAM POSITIVE
Has a thick peptidoglycan layer
90% of the Gram-positive cell wall is comprised of peptidoglycan
two types of teichoic acids
GRAM POSITIVE
1) Lipoteichoic acid
on the surface, embedded in the peptidoglycan layer
linked to the cytoplasmic membrane
2) Wall teichoic acid
on the surface
linked to only the peptidoglycan layer
GRAM NEGATIVE
cell wall of Gram-negative bacteria is much thinner
comprised of only 20% peptidoglycan
have two unique regions which surround the outer plasma membrane:
1) periplasmic space
2) lipopolysaccharide layer
lipopolysaccharide layer
a thin peptidoglycan layer
an outer membrane attached to the peptidoglycan layer by lipoproteins
the outer membrane is made of protein, phospholipid and lipopolysaccharide
the lipid portion is embedded in the phospholipid
The lipid is toxic
The cell wall has channels called Porins for the transport of low molecular
weight substances
periplasmic space
between the cytoplasmic membrane and the cell wall
hydrolytic enzymes
antibiotic inactivating enzymes
transport proteins
Strong negative charge assists in:
evading phagocytosis
evade the complement system
provides increased barrier to:
antibiotics, lysozymes, detergents
provides more attachment sites for:
virus
harmful substances
more susceptible to mechanical breakage
lipid A endotoxin is toxic to host
CELL WALL
the cell wall is not a regulatory structure like the cell membrane
though it is porous, it is not selectively permeable and will let anything pass that can
fit through its gaps
EXTRACELLULAR MATRIX
attached to the cell wall
made of polysaccharide or polypeptide, or a combination of both
form a viscous layer
capsule
slime layer
CAPSULE
thick, structured and adheres strongly to the cell wall
Adhere to surfaces to form colonies
Antiphagocytic
Antigenic
Protect the organism from dehydration
SLIME LAYER
disorganized and loosely attached to the cell wall
Staphylococcus mutans
causes dental caries
MOVEMENT
Flagellum
Made of the protein flagellin
rotation is for swimming towards an attractant
water is as viscous as syrup for a bacteria
able to move 50 microns/sec
100X bacterial body length/sec
fish able to swim only 10X body length/sec
Axial Filaments
found in Spirochetes
similar to flagella
attached throughout the body length
PILI
made of the protein pilin
virulence factors
project from the cell surface
Conjugation Pili
for the transfer of extrachromosomal DNA between donor and recipient
FIMBRIAE
used for attachment to surfaces
more numerous than pili
CYTOPLASMIC STRUCTURES
Nucleoid
area of concentrated DNA
no nuclear membrane
The DNA is single circular
double stranded without proteins
CYTOPLASMIC STRUCTURES
Ribosomes
cytoplasmic, not attached to organelles
Plasmids
Extrachromosomal loops of DNA
some code for drug resistance
toxins
ENDOSPORES
Metabolically inactive
may produce endospores under environmental stress
lack of water
lack of nutrients
severe temperature changes
Clostridium
Bacillus
Spores can be dormant for many years
can survive
extreme heat
desiccation
radiation
toxic chemicals
when conditions become favorable they revert to an active state
Spore germination is activated by heat in the presence of moistures
END CELL BIOLOGY OF BACTERIA