Transcript Bacteria - LiveText

Chapter 23: Bacteria
Archaea and Bacteria
Kingdom Archaebacteria – the most primitive organisms
(archae = ancient)
live in harsh conditions including
- acidic hot springs
- very salty water
- environments with no oxygen
- near undersea volcanic vents
- different from other bacteria
- cell wall composition (pseudomurien)
- Cell membrane
- rRNA
Phyla 1: Methanogens:
- obligate anaerobes (oxygen kills them)
- metabolizes hydrogen gas and CO2 to methane gas
- live in the bottom of swamps, sewage, and inside the
digestive tracks of many animals
Helps
- grazing animals process cellulose
- termites process wood
- in industry to treat sewage, purify water.
Phyla 2: Thermoacidiphiles
- can live in extremely hot and
acidic water or deep in the
ocean near hydrothermal vents
in the ocean floor
- Ex: hot springs of
Yellowstone Natl Park
- chemotrophs = process sulfur
compounds to produce energy
Phyla 3: Halophiles:
- live in extremely
salty (saline)
environments,
ex: Dead Sea
- use the salt to
generate ATP.
Phyla 4: Psychrophiles
- live in
temperatures
below 15C
- Found mostly
in the Arctic
and Antarctic
oceans sea
ice.
Kingdom Eubacteria
(Eu = true) “Germs”
Characteristics used for classifying:
1) Composition of the cell wall –
identified with Gram staining technique
Gram positive – stains purple – thick
outer layer of peptidoglycan
Gram negative – stains pink/red – lipid
layer covering thin layer of peptidoglycan
Peptidoglycan – a protein-carbohydrate
compound
2. Method of getting energy: autotrophic (chemotroph,
phototroph), heterotrophic
3) Type of metabolism
obligate aerobe – must have oxygen; dies without it
obligate anaerobe – dies if exposed to oxygen; processes
ATP by fermentation
facultative anaerobe – uses oxygen
when it can but doesn’t need it
4) Shape of bacterial cells
round
coccus (cocci)
rod shaped
bacillus (bacilli)
spiral shaped
spirillus
5) How cells grow (prefixes)
a) staphylo – clumps
b) strepto - chains
c) diplo - pairs
6) Motility – movement
a) flagellated – move with flagellum or
flagella
b) slime layer allows gliding
c) spirochete - cork-screw rotation
A)
Proteobacteria
• may have symbiotic lifestyle
• ex. Nitrogen fixing bacteria
inside legumes (ex: beans)
• In human and animal
intestines, help break down
foods (enteric bacteria)
• Some in soil or fresh water
and process iron and other
minerals as an energy
source (chemotrophs)
B) Gram positive
- thick outer layer of peptidoglycan (stains purple)
- may be beneficial or cause disease
- may be used to make yogurt, pickles, and buttermilk
- or to make medicines using biotechnology
Ex. Strep throat ; staph infections; tuberculosis
C) Cyanobacteria
• Gram-negative
• contain chlorophyll (but not
chloroplasts), perform a
plant-like photosynthesis
releasing oxygen as a byproduct
• Ex. Filamentous bacteria
(grow in stagnant water)
D) Spirochetes
- gram negative
- spiral shaped
E) Chlamydia (no peptidoglycan)
- gram negative
- round shape
- are parasites to animal cells
Reproduction – 2 types
Asexual - most common
Binary fission – divides into two new cells
Sexual – exchanges genetic info giving variation
a)
conjugation
- two bacterial cells connect with a hair-like “pili”
- info is passed through the tube
b)
transformation
– living bacteria absorbs dead related bacterial DNA
and incorporates it into it’s own genome
c)
transduction
– a virus transfers DNA
Endospores
- special dehydrated cells formed by some bacteria
to survive bad living conditions
- ex: high temperatures
- when conditions improve cell is revived
Bacteria and Disease
Toxins – poisons produced by some bacteria
1) endotoxin
- created inside the bacterial cell
- released as the cell dies
- usually Gram neg.
2) exotoxin
- secreted by living bacterial cell into surrounding
environment (host)
- usually Gram-positive
Pathogens – bacteria that cause disease
Antibiotics
- chemicals that kill bacteria by interfering with
cellular functions such as protein or cell wall
synthesis
- Gram positive bacteria that cause
disease need
different antibiotics than Gram
negative bacteria
Broad spectrum antibiotics affect a wide variety of
bacteria within the taxa
Antibiotic Resistance in Bacteria
• most of the population dies, some survive
• Survivors reproduce and are no longer affected by
antibiotic