Download Bacteria RTN 470-477

Bacteria RTN 470-477
Robert Hooke, van Leeuwenhoek: invention of microscope(17th
century) first to observe bacteria
Prokaryotes – unicellular organisms that lack a nucleus = bacteria
Size = 1-5 micrometers (1 micrometer = 1 millionth of
meter) most smaller than eukaryotes (cells with nucleus)
CLASSIFYING PROKARYOTES(BACTERIA)
Monera – Old grouping
Eubacteria separate kingdom than Archaebacteria
Domain – a level of classification higher than a kingdom; some
biologist think that the 2 types of bacteria are so fundamentally
different that they should be in their own domain
EUBACTERIA
 Larger of the 2 kingdoms of bacteria
 Habitat = fresh water, salt water, land, on and within
the human body
o Example: Escherichia coli – found in human
intestine
 Cell wall – determines bacteria’s shape/protects
o Peptidoglycan= carbohydrate
o Pili – involved in cell to cell contact
o Flagella used for movement
Cell membrane – surrounds cytoplasm - contains
ribosomes- and DNA
See figure 19-2
ARCHAEBACTERIA
 Do not have the peptidoglycan found in eubacteria
 Different membrane lipids
 DNA sequences of genes more like eukaryotes than
eubacteria
 Think that archaebacteria are more closely related to
eukaryotes
 Habitat – extremely harsh
o Methanogens – oxygen free areas - guts of
animals, thick mud, produce methane gas
o Salty environments
o Hot springs
Identifying Prokaryotes
Shape,
Rod shaped = bacilli
Spherical = cocci
Spiral, corkscrew = spirilla
chemical nature of cell walls,
Gram stain – primary = violet
Peptidoglycan(thick layer) absorbs violet color – then
wash with alcohol, and stain persists = gram +
Gram - = peptidoglycan(thin layer) surrounded by lipid
layer – lipid dissolved by alcohol – thus stain is washed out of
peptidoglycan layer - appear pink or light red
Movement –
No movement
Flagella propelled
Lash, snake, spiral forward
Glide smoothly
Metabolic Diversity – best means of identifying different bacteria
HETEROTROPHS – Most bacteria
Obtain E by consuming organic molecules made by
other organisms need carbon
 Chemoheterotrophs – most animals are
chemoheterotrophs
 Photoheterotrophs – photosynthetic, and need organic
compounds for carbon source
AUTOTROPHS Photoautotrophs – use light E to convert CO2 + water
to carbon compounds and oxygen – just like plants
 Found in upper surfaces of water bodies
 Cyanobacteria – bluish pigment and chlorophyll a – key
pigment in photosynthesis – UBIQUITOUS – first
colonizing species “black” ring around rocks at ocean
or lake edge
 Chemoautotrophs – make organic carbon molecules
from Carbon dioxide – NO LIGHT- use chemical
reactions involving ammonia, hydrogen sulfide, nitrites,
sulfur or iron as E source - some live in ocean vents –
obtain E from hydrogen sulfide gas from hydrothermal
vents on deep ocean floor
RELEASING ENERGY
Energy is released by: cellular respiration, fermentation or
both
OBLIGATE AEROBES – require Oxygen example –
Mycobacterium tuberculosis
OBLIGATE ANAEROBES – no oxygen – oxygen can kill
OBLIGATE ANAEROBES(cont)
Ex – Clostridium botulinum – found in soil or can grow
in canned food that was not sterilized (BOTOX)
FACULTATIVE ANAEROBES - don’t require Oxygen ,
but are not harmed by oxygen - can switch between cellular
respiration( oxygen present) - fermentation(oxygen absent) – can
live ANYWHERE Example – Escherichia coli – anaerobic in our
intestine; aerobic in contaminated water
GROWTH AND REPRODUCTION
FOOD availability and Waste production limit the growth of
bacteria (which can be as fast as every 20 minutes!!)
BINARY FISSION – DNA replicated and cell divides
2 identical daughter cells
Asexual since no exchange or recombination of
DNA
CONJUGATION - DNA is exchanged
Hollow bridge forms between 2 cells
Allows for genetic diversity in population
SPORE FORMATION – when growth is unfavorable spores are
formed = ENDOSPORE – remain dormant for long periods,
Ex; Bacillus anthracis – “anthrax”
IMPORTANCE OF BACTERIA
Bacteria are vital to maintaining the living world
Producers – capture E by photosynthesis
Decomposers – break down nutrients in dead matter
Human use
Decomposers – bacteria – recycle nutrients back into ecosystem
Decomposers (cont) – break down complex compounds in sewage,
to produce pure water, nitrogen and Carbon dioxide gases,
and products to make fertilizers
NITROGEN FIXERS – (remember the nitrogen cycle??)
Plants need N to make amino acids (protein synthesis)
N gas = 80% atmosphere not usable by most organisms
Bacteria can transform Ngas into NH3 (ammonia) = nitrogen
fixation –
SYMBIOTIC RELATIONSHIP OF plants and N fixing bacteria
Example – legumes, soybeans, host Rhizobium bacteria
Grows in nodules or knobs on roots – both organisms
benefit (symbiosis)
HUMAN USES of Bacteria
Bacteria used in production of foods and beverages
Used in Industry
Digests petroleum – for use in oil spills
Removal of waste and poison in water
Mine minerals
Synthesize drugs and chemicals through genetic
engineering(insulin production)
E.coli – in human colon(thus its name) synthesize vit K for
us( calcium absorption, blood clotting)
Biotechnology – archaebacteria – extreme environment
bacteria – produce heat stable enzymes – used in medicine, food
production industrial chemistry