Bacteria and Archaea
Prokaryotic organisms
Premedical - Biology
They are (almost) everyvwhere!
• Their history starts 3,5 billions years ago
• Dominate the biosphere
• Inhabit the human mouth or skin, digestive
system – 500 – 1,000 species
• Only minority ot them cause disease in
humans or any other organism
• They are able to adapt in structure and
function, in nutrition and metabolism
• Reproduction, mutation and genetic
recombinatoin promote genetic diversity
Bacterial structure
Prokaryotes
• unicellular
groups of two or more cells,
true colonies
• sphere (cocci)
rods (bacilli),
helices (spirilla, spirochetes)
• 0.5-5μm
(10-100μm for eukaryotic cells)
Staphylococcus aureus
Cell walls
• protection (hypotonic enviroment)
would die in hypertonic medium (heavily salted meat)
• different from plant, fungi, protists cell walls
• peptidoglycan (polymers of sugar cross-linked by short
peptides that vary from species to species)
• Tool in microbial taxonomy is Gram stain – separate
into two groups based on differencies in cell walls
• Gram positive – large amount of peptidoglycan
• Gram negative – less peptidoglycan, outer membrane
of lipopolysaccharides (LPS), carbohydrates bonded
to lipids, Lipoteichoic acids (LTA)
Gram positive and Gram negative
Patogenity
• Gram negative are more threatening
• LPS of negative are often toxic
• Outer membrane is protect against hosts and antibiotics
• Antibiotics, like penicillins, inhibit synthesis of crosslinks in peptidoglykan and prevent the formation
• Capsule - adherention to substrate, protection, gelatinous
glue the cells to colonies
• Pili, pilus - adherention, to mucous
membrane, conjugation – DNA transfer
• some product antibiotics
Pathogenic prokaryotes
Cause about one half of all human diseases
Some pathogen are opportunistic
– normal residents of a host, but can cause illness,
when the host‘s defences are weakened.
Pathogen caused illnesses by producing
Exotoxins: proteins secreted by prokaryotes, (botulism,
cholera)
Endotoxins – components of the outer membranes of
certain Gram-negative bacteria (Salmonella)
Movement
movement – 100 times their body length per
second
• Flagelar action - most common mechanism, scattered
over the entire cell surface or at one or both
ends of the cell
The flagella of prokaryotes
and eukaryotes differ
in function and structure
• directional
• motility of spirochetes
– two or several helical
filaments under the outer
sheath of the cell
• taxis movement – toward
or away from stimulus
chemotaxis
phototaxis
Genomic organization
• Not true nuclei enclosed by membranes
• Not compartmentalization by internal membrane systems
• DNA is concentrated in nucleoid region – prokaryotic
chromosome – one double stranded molecule
in the form of ring
• essential functions programmed by chromosome
• small rings of DNA – plasmids – resistance to
antibiotics, metabolism of unusual nutrients
Replicate independently of the main chromosome
Division
• binary fission – „division in half“
generation time is measured in minutes or hours
• bacterial chromosome is attached to the plasma membrane
Grow of populations
• temperature, pH, salt concentrations, nutrient sources
• More multiplication of cells than to the enlargement of
individual cells
• Generation time in the range of 1 to 3 hours, number of
cells doubling with each generation
During lag phase, bakteria adapt
themselves to growth conditions
Exponential phase is a period
characterized by cell doubling
During stationary phase,
a result of nutrient depletion
and accumulation of toxic products
At death phase, bacteria run out of nutrients and die
Endospores
-The ability of some prokaryotes to withstand hard
conditions
- The cell replicates chromosome, the copy became
surrounded by a durable wall, outer cell disintegrates,
endospore contained survives all sorts of trauma:
lack of water, nutrients, extreme heat or cold, almost poisons
Clostridium tetani
Bacillus cereus, Bacillus subtilis.
(1, 4) central endospore; 2, 3, 5) terminal
endospore; (6) lateral endospore
Sporulation
Grow of populations
• prokaryotes lack sexual cycle, important source
of genetic variation
• Three mechanisms of genetic recombination
Transformation – genes are taken up from surrounding
environment
Conjugation – genes are transferred directly from one
to another
Transduction – genes are transferred
between prokarytoes
by viruses
Bacterial transformation
• naked DNA passess into recipient cells,
• Griffith (1928) 1. experiment
• Avery, McLeod, McCarthy
• (1944) – the same effect with isolated DNA
• finally homologous recombination:
the exchange of homologous parts
Transduction
• Bacteriophages transmit spontaneously bacterial
genes
• Special – restrictions mistakes within cutting out of
bacteriophage from bact. genome
• General – into small parts of phages particles is packed
bacterial DNA instead of phages one
Bacterial conjugation
• Donor’s plasmid F+ passes into acceptor’s cell F-,
• Conjugation by cytoplasmatic conjugative bridge
• there is the exchange of homologous parts
How an organism obtain two resources for
synthesizing organic compounds: energy and a
source of carbon
Marine
and halophilic prok.
plants
algae
Certain
prokaryotes
Fungi, animals,
most protist,
Photoautotrophs
use light-energy to drive synthesis of organic compounds from carbon
dioxide; internal membranes with light-harvesting pigment systems;
Chemoautotrophs
need only CO2 as a carbon source, obtain energy by oxidizing inorganic
substances: hydrogen sulfide (H2S), ammonia (NH3), ferrous ions (Fe2+)
Photoheterotrophs
use light-energy to generate ATP, but must obtain carbon in organic form;
Chemoheterotrophs
must consume organic molecules for both energy and carbon
Metabolism
• Metabolic diversity is greater among prokaryotes
than all eukaryotes combined.
• Able to use various organic and inorganic
molecules from the atmosphere (CO2, N2)
• Primary metabolism: anaerobic, heterotrophic
than autotrophic
Anaerobic bacteria - some disappeared, inhabition
anaerobic environments, symbiosis, parasitism
Many prokaryotes are symbiotic
Symbiosis „living together“- ecological relationships
between organissm of different species that are in direct
contact; symbionts – if one is much larger than the other,
the larger is termed host
Mutualism - both symbionts benefit
Commensalism - one symbionts receive benefits while
neither harming nor helping the other in any significant way
Parasitism – one symbiont, called a parasite, benefits at the
expense of the host; patogene
Metabolic relantioship to oxygen
Obligate aerobs – cellular respiration
Facultative anaerobs – if it is present, use it. They
use fermentation in an anaerobic enviroment
Obligate anaerobs are poisoned by oxygen, use
fermentation or extract energy
by anaerobic respiration – inorganic molecules
accept electrons
Autotrophic Bacteria
• organism that makes organic compounds from
inorganic sources
• synthesize organic compounds from carbon dioxide and
other inorganic elements (CO2, H2S) or molecules
• using either light energy or chemical energy.
• green sulphur bacteria, purple sul-phur bacteria and the
purple norisulphur bacteria,
Heterotrophic Bacteria
• the majority are chemoheterotrophs
• organism that cannot make organic compounds from
inorganic sources.
• They depend on small or large molecules which they
have to absorb.
• There are three types of heterotrophic bacteria :
saprophytic or saprobic, parasitic and symbiotic.
Pseudomonas, Staphylococus, Escherichia coli
Prokaryotes, Archae and Eubacteria
Common ancestor 3,5 bilion years ago
Archae
– Two
branches of prokaryotic evolution were identified by comparing
ribosomal (16S-rRNA) RNA and completely sequences genomes of several
extant species.
– Archaea inhabit extreme inviroments, hot
springs and salt ponds
– Archea have at least as much in common
with eukaryotes as they do with bacteria;
have many unique traits.
Phylogeny of prokaryotes
domain Archea
Methanogens – unique form of energy metablism, H2 is used
to reduce CO2 to methane CH4. Oxygen is a poison. Live in
swamps and marshes and other species inhabit the gut of
animals.
Extreme halophiles – live in saline places as the Great Salt
Lake and the Dead sea
Extreme thermophiles – thrive in hot enviroments,
temperatures are of 60°C to 80°C, thermal springs
Research and technology
Simple model systems
Escherichia coli – the prokaryotic „ white rat“
Soil bacteria called pseudomonas decompose
pesticides, petroleum componeds and other.
The food industry uses bacteria to convert milk to
yogurt and various kind of cheese.
Gram stain of yogurt, 1000x
with Lactobacillus acidiphilus
Most widely known pathogenic bacteria:
Borrelia burgdorferi – Lyme disease
Treponema pallidum - syphilis
Neisseria gonorrhoeae - gonorrhoea
Neisseria meningitis – cerebro-spinal meningitis
Salmonella typhi – typhus
Bordetella pertusis – whooping cough
Staphylococcus aureus – skin suppuration
Staphylococcus pneumonie – pneumonia
Streptococcus pyogenes – angina, sore throat
Streptococcus pneumonie – pneumonia
Clostridium tetani - tetanus
Clostridium botulinum- botulism
Bacillus anthracis - anthrax
Mycoplasma pneumonie – pneumonia
Shigella dysenterie- red pestilence, dysentery
Vibrio cholerae – cholera
Mycobacterium leprae - leprosy
Mycobacterium tuberculosis - tuberkulosis
Corynebacterium diphterie - diphtheria
Haemophilus influenzae – inflammation of airways
Rickettsia prowazeki - spotted fever
Pasteurella (Versinia) pestis – plague
Francisella tularensis - tularemia
Campbell, Neil A., Reece, Jane B., Cain Michael L., Jackson,
Robert B., Minorsky, Peter V., Biology, Benjamin-Cummings
Publishing Company, 1996 –2010.