Download Bacteria - Arrowhead Union High School

BACTERIA
Kingdom Eubacteria in 23 slides
Kingdom Eubacteria
 Normal, everyday bacteria &
photosynthetic bacteria
 Unicellular
 Small—0.5 to 1.5 micrometers
Structure
 Prokaryotic
 No organized nucleus—DNA is free-floating in
the cytoplasm
 No membrane-bound organelles
 Many enzymes are attached to the
plasma membrane
 Ribosomes are the only cytoplasmic
organelles—smaller than eukaryotic
ribosomes
Structure
ribosomes
cytoplasm
DNA
Plasma membrane
Cell wall
capsule
(in some species)
Capsule
 A gelatinous covering found on some species
of bacteria
 Contributes to virulence
 Protect pathogenic bacteria from
phagocytosis by cells of the host
Cell Wall
 Strong and semi-rigid
 Gives the cell its shape
 Protects cell from changes in moisture and
the actions of many drugs
 Penicillin stops the formation of the cell wall
in bacteria
Plasma membrane
 In prokaryotes, consists primarily of
phospholipids and proteins
 Phospholipid bilayer with integral &
peripheral proteins
 Selectively permeable
DNA
 A single long circular molecule of DNA—the
bacterial chromosome
 Carries all the information required for the
cell’s structures & functions
 In actively growing bacteria, as much as 20%
of cell volume is occupied by DNA
Plasmid DNA
 Small, circular DNA molecules
 Usually carry from 5 to 100 genes
 Generally not for the survival of the
bacterium under normal environmental
conditions
Ribosomes
 Site of protein synthesis
 A bacterial cell will have tens of thousands
Bacterial Cell Extensions
 Pili—submicroscopic hair-like structures
(bristles)
 Allow bacteria to stick to surfaces & to each other
(ex.—E. coli)
 Flagella—long protein extensions of the cell
(tail)
 Used for movement
Shapes
 All known species of bacteria are one of three
basic shapes:
bacillus
coccus
spirillum
SUCCESS!!!
 In terms of numbers and distribution…the
most successful organism on the planet!
 WHY???
 Reproduce rapidly
 Some live in and/or feed on materials that are
poisonous to anything else
 Can exist under extreme conditions
 High rate of mutation makes them very adaptable
and very difficult to get rid of
Ecology
 Found in every habitat
 Each square inch of your skin has about
100,000 bacteria!
Consumers
 Consumersdepend on other organisms for
food
 Saprobe—gets energy from dead &/or dieing
organisms (plant/animal/&c.)
 decomposers
 =nature’s recyclers…recycle nutrients
Producers
 Photosynthetic bacteria
 Produce own food using sunlight & inorganic
materials
 Chemosynthetic bacteria
 Use a photosynthesis-like process using sulfur &
iron compounds (thermal deep sea volcanic vents)
Oxygen requirements
 Obligate aerobe
 Must have free oxygen (O2)
 Obligate anaerobe
 Can not live in the presence of free oxygen
 Facultative anaerobe
 Can grow with or without free oxygen
Importance of bacteria
 Disease—tetanus, gas gangrene, Salmonella,
bubonic plague, strep throat, tuberculosis,
botulism, Lyme disease, syphilis, &c.
 Food—cheese, yogurt, sour cream, pickles,
sauerkraut, &c.
 Industry—clean up oil spills, produce medicines,
genetic material, snow making, &c.
 Environmental—recycle nutrients, break down
dead tissue, base of much of food chain,
symbiotic with many species of organisms…
Reproduction
bacterial
cell
DNA
replicates
DNA splits
Cell wall
pinches
= asexual reproduction
(a- = without, not)
BUT…if bacteria are asexual, doesn’t
that mean that they will always stay
the same? How do they adapt to new
environmental situations?????
two new
genetically
identical cells
Bacterial change???
 Epigenetic factors—tweak the active genes
 Mutation
 Bacteria have a high rate of mutation (permanent
change in the DNA of an organism)
 Horizontal Gene Transfer
 Transposons