Bacteria and ArchaeaProkaryotic 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 cross-

links 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• directional 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 cellThe flagella of prokaryotes and eukaryotes differ in function and structure

• 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

plants algae

Certain prokaryotes

Marine and halophilic prok.

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

• 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

Metabolism

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

Many prokaryotes are symbiotic

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

– 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.

Archae

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, 1000xwith Lactobacillus acidiphilus

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

Most widely known pathogenic bacteria:

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.