Bacterial cytoplasm, endospores, motility & flagella Bacterial ...

Bacterial cytoplasm,
endospores, motility & flagella

Within the cytoplasm
Genetic material
➤Chromosome
➤Plasmids
Ribosomes
Storage bodies and inclusions

Bacteria generally have a
single large chromosome
Genetic Material
It is not bounded by a
membrane
Nucleoid

Plasmids
Extrachromosomal circular DNA
Plasmids in a bacterial host cell. A
cell may contain no plasmids, , one
plasmid or many copies of a
plasmid. A single host may contain
a number of different plasmids.
• Contain genes which are not
necessary for the organism’s
survival but which may be useful to
it (e.g antibiotic resistance genes,
genes for enzymes which degrade
pollutants for consumption by the
cell, etc.).
• Can be transferred ‘horizontally’
(from mature cell to mature cell)
http://www.wsu
wsu.edu:8080/~
:8080/~hurlbert/pages/Chap9.html#Plasmids

Plasmids (cont.)
Used as vectors for transferring DNA in
genetic engineering
Electron micrograph of pCMVLuc
plasmid DNA
http://www.qiagen
qiagen.com/catalog/Fig6_1.html

Ribosomes
Used for constructing proteins from messenger
RNA (mRNA)) (more on this later)
In two parts and made up of proteins and ribosomal
RNA (rRNA)

Storage bodies and inclusions: PHB,
glycogen, sulfur, magnetosomes
poly β-hydroxybutyrate
(PHB) granules

Endospores
• Formed for
survival, not
reproduction
• Toughest,
most resistant
life form of all
due to
presence of
dipicolinic
acid in the
spore coat

250 Million Year Old Bug Unearthed and Regrown
by Dan Ferber
Deep within salt crystals trapped for eons
below a New Mexico desert, researchers
found a 250-million-year-old strain of
bacteria. The bacterium, reported at the
annual American Society for Microbiology,
is ten times older than the oldest known
bacterium. The ancient strain could offer
scientists new insights into the state of
bacterial evolution from a time before the
dinosaurs.
The new strain was recovered from brine pockets in salt crystals known as chevrons, said
microbiologist Russell Vreeland of West Chester University, West Chester, Pennsylvania.
The crystals were found in a geological formation half a mile below the New Mexico desert,
in tunnels dug more than 20 years ago to dispose of low-level radioactive waste, he said.

Endospores (cont.)
Formed within cell (endo(
= inside) unlike fungal spores

Endospore germination

Significance of Endospores
Two major genera have them: Bacillus and
Clostridium.
➤Bacillus anthracis -- causal agent of anthrax
➤Clostridium tetani -- causal agent of tetanus
➤C. perfringens -- causal agent of gas gangrene
➤C. botulinum -- causal agent of botulism
Persistence and resistance of endospores
contribute to the pathogenicity of these
species.

Peritrichous flagella
Bacterial Motility

Polar flagella

Run and tumble motility

Run and tumble motility

In the presence of an attractant, runs become longer and
tumbles fewer, thus effectively propelling the cell toward
the attractant. This phenomenon is known as chemotaxis.

The bacterial flagellum

Eukaryotic motility structures
•Flagella
and cilia are similar in composition but differ in size and function
•Flagella found singly or in pairs at the
end of some protozoa and algae
•Larger than bacterial flagella
•Move in a whip-like manner rather
than rotation of prokaryotic flagella
•Cilia only found in ciliates, , a type of
protozoan.
•Shorter, more numerous than flagella (of
eukaryotes)
•Function like oars: beat in synchrony to
move cell (or to draw in food particles)

Eukaryotic Motility

Why don’t prokaryotes have
membrane-bound organelles
One answer: they may not need them

One reason for internal membranous
structures in eukaryotes: surface/volume ratio
A smaller cell has more efficient exchange with its surroundings because
it has more membrane surface area for its volume

Thus, internal membranes may be needed for
efficient transport (and
compartmentalization) inside eukaryotic
cells because their volume is great relative
to their surface.
In simpler words, more of the inside of a
prokaryotic cell is closer to the surface
(where exchange of nutrients and waste
occurs) than is the case in eukaryotes. . Thus,
membranous structures are needed for
movement and storage.