And Bacterial Creepers
I study the lives on a leaf:the little
Sleepers, numb nudgers in cold dimensions
Beetles in caves, newts, stone-deaf fishes,
Lice tethered to long limp subterranean weeds,
Squirmers in bogs,
And bacterial creepers
Theodore Roethke
The Bacteria
 Phylum: Schizomycetes
 Cells are prokaryotic and amongst the
smallest known cells ( length 0.5-20 µm ).
 No membrane bound nucleus.
 Have ribosomes,but no other organelles.
 DNA present as a long circular molecule.
 ( see handout for bacterial structure)
Habitat
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Bacteria are found everywhere.
Air
Water
Soil
On plants and animals.
In plants and animals.
Types of Bacteria
 There are three major
groups of bacteria
based on their shapes;
coccus, bacillus, and
spirillum.
1. Coccus
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Plural is cocci.
Spherical bacterium
Single cells - monococci
Pairs - diplococci
Chains - streptococci
2.Bacillus
 Plural is bacilli.
 A rod - shaped bacterium.
 Exists as single cells, in
pairs (diplobacilli), and in
chains (streptobacilli).
3. Spirillum
 Plural is spirilli.
 A spiral - shaped
bacterium.
 Exist only as single
cells.
Bacterial Structure
 Cell Wall - outermost
structure of the cell.
 Made up of a substance
called peptidoglycan ( a long
chain of sugars linked to
amino acids ).
 Penicillin destroys bacteria
by interfering with the
peptidoglycan molecules.
Bacterial Structure Continued
 Cell Membrane - Found
beneath the cell wall.
 May be folded inward.
 ATP production (energy),
takes place on the folds of
the membrane.
Bacterial Structure Continued
 Capsule: This is a layer of
slime secreted over the cell
wall of the bacterium.
 The capsule provides
protection for the bacterium.
 Bacteria that have capsules
are said to be encapsulated.
 Most pathogenic bacteria are
encapsulated.
Bacterial Structure Continued
 Flagella - Some bacteria in
the bacilli and spirilli
categories can move by way
of flagella ( whip - like
structures that propel the
bacteria).
 Note: Cocci do not have
flagella.
Bacterial Physiology-O2 Needs
 Some bacteria need O2 and
others do not.
 Aerobic Bacteria: Need O2 for
cellular respiration.
 Facultative Anaerobes: Can
live in the presence or absence
of O2.
 Obligate Anaerobes: Can live
in the absence of . O2 only. An
example is Clostridium.
Bacterial Physiology-Nutritional
Needs
 Like all living things bacteria need food.
 Bacteria are placed in one of two categories,
depending on how they get their food.
 The two categories are: Heterotrophic
bacteria and Autotrophic bacteria.
Heterotrophic Bacteria
 Heterotrophs must get their
food from a source of preformed organic matter:
 (A) Saprobes- feed on the
remains of dead plants and
animals.
 (B) Parasites - live on or in
the organism and cause
disease. For example,
Mycobacterium tuberculosis.
Autotrophic Bacteria
 Autotrophs can make their
own food:
 Photosynthetic-use a special
type of chlorophyll called
bacteriochlorophyll.
 O2 is not released in bacterial
photosynthesis
 Chemosynthetic -obtain
energy by breaking down
inorganic material such as
iron or sulfur.
Bacterial PhysiologyReproduction
 The growth of bacteria is limited by the
following factors:
 temperature
 pH
 moisture content
 nutrient availability
 competition from other organisms
Bacterial PhysiologyReproduction continued
 Bacteria reproduce
asexually by binary
fission. Using this
process bacteria
reproduce about
every 20 minutes.
Bacterial PhysiologyReproduction continued
 The rate of reproduction
can be plotted in a
graph called a Growth
Curve.
 Under ideal conditions
one bacterial cell can
produce a mass of 2
million Kg in 24 hours.
 In reality this never
happens. Why?