Domain (Kingdom) Bacteria, Domain (Kingdom) Archaea, and Viruses

Chapter 17

Outline

Introduction Features of Kingdoms (Domains) Bacteria and Archaea Domain Bacteria (Kingdom Bacteria) – The True Bacteria Human Relevance of the Unpigmented Purple, and Green

Sulfur Bacteria Class Cyanobacteriae – The Cyanobacteria (Blue-Green

Bacteria) Class Prochlorobacteriae – The Prochlorobacteria Kingdom Archaea (Domain Archaea) – The

Archaebacteria Viruses Viroids and Prions

Introduction Fossils of bacteria - 3.5 billion years old Fossils of 1st eukaryotic cells - 1.3 billion years

old 5,000 species of bacteria recognized today• Each species found in astronomical numbers−Difficult to classify simple one-celled

organisms = # of bacteria species uncertain−Strains of one species look alike

Clustered by what they do

Features of Kingdoms (Domains) Bacteria and Archaea

All have prokaryotic cells• No nuclear envelopes• Have long circular strand

of DNA, ribosomes, membranes and plasmids• No membrane-bound

organelles, such as plastids, mitochondria, dictyosomes, endoplasmic reticulum Section of Prochloron cell

Features of Kingdoms (Domains) Bacteria and Archaea

Nutrition• Primarily by absorption of food in solution through cell

wall• Some by chemical reactions or by photosynthesis

Reproduction predominately asexual, by fission• Fission - no mitosis, DNA strand duplicates and

distributed to new cells No sexual reproduction– Genetic recombination facilitated by pili or by close

contact of cells

Features of Kingdoms (Domains) Bacteria and Archaea Cellular Detail and Reproduction of Bacteria

Folds of plasma and other membranes perform some of functions of organelles in eukaryotic cells

Ribosomes present, but about ½ size of eukaryotic cells

Nucleoid - single chromosome in form of ring

30 or 40 plasmids may be present• Plasmids - small circular DNA molecules that replicate

independently of chromosome

• Entire complement of plasmids consists of multiple copies of one or few different DNA molecules

Features of Kingdoms (Domains) Bacteria and Archaea Cellular Detail and Reproduction of Bacteria

Mitosis does not occur Fission• 2 copies of duplicated chromosomes migrate to

opposite ends of cell• Perpendicular walls and cell membranes formed in

middle of cell• 2 new cells separate and enlarge to original size

Replication of nucleoid

Fission cont’d.• May undergo fission every 10 - 20 minutes under ideal

conditions−Usually exhaust food supplies and accumulate

wastes

New wall growing inward of dividing bacterial cell

Features of Kingdoms (Domains) Bacteria and Archaea Cellular Detail and Reproduction of Bacteria

No gametes or zygotes, and no meiosis 3 Forms of Genetic Recombination:

• Conjugation - DNA transferred from donor cell to recipient cell usually through pilus (plural: pili)

• Transformation - living cell acquires DNA fragments released by dead cells

• Transduction - DNA fragments carried from one cell to another by viruses

Features of Kingdoms (Domains) Bacteria and Archaea Cellular Detail and Reproduction of Bacteria

Conjugation

Most bacteria >2 or 3 μm in diameter Occur in 3 forms:

Features of Kingdoms (Domains) Bacteria and Archaea Size, Form, and Classification of Bacteria

CocciSpherical or

elliptical

BacilliRod-shaped or

cylindrical

SpirillaHelix or spiral

Also classified by:• Presence of sheath around cells, hair-like or

bud-like appendages, endospores, pili or flagella • Color• Mechanisms of movement• Biochemical characteristics• Reaction of cell walls to dye−Gram-negative−Gram-positive

Features of Kingdoms (Domains) Bacteria and Archaea Size, Form, and Classification of Bacteria

Domain Bacteria (Kingdom Bacteria) – The True Bacteria

True bacteria have muramic acid in cell walls, and different from archaebacteria in RNA bases, metabolism and lipids

Phylum Bacteriophyta• Class Bacteriae - unpigmented, purple, and green sulfur

bacteria−Most heterotrophic - cannot synthesize own food

Majority saprobes - food from nonliving organic matter

Some parasites - depend on living organisms for food

Domain Bacteria (Kingdom Bacteria) – The True Bacteria

Phylum Bacteriophyta• Autotrophic Bacteria - synthesize organic compounds from

simple inorganic substances−Photosynthetic without producing O2

Purple Sulfur Bacteria - bacteriochlorophyll pigments, use H2S

Purple Nonsulfur Bacteria - bacteriochlorophyll pigments, use H2

Green Sulfur Bacteria - chlorobium chlorophyll pigments, use H2S

−Photosynthetic and produce O2

Cyanobacteria and Chloroxybacteria

Domain Bacteria (Kingdom Bacteria) – The True Bacteria

Phylum Bacteriophyta• Autotrophic bacteria cont’d.

−Chemotrophic Bacteria - obtain energy from various compounds or elements through oxidation Iron Bacteria - transform soluble Fe to insoluble

Sulfur Bacteria - convert H2S gas to S or S to SO42-

Hydrogen Bacteria – use H2 derived from anaerobic or N2-fixing bacteria

Human Relevance of the Unpigmented, Purple, and Green Sulfur Bacteria

Composting and compost• Bacteria decompose organic waste to form compost

• Modes of access of disease bacteria– Air Coughs, sneezes - saliva droplets contain bacteria Diphtheria, whooping cough, some meningitis

forms, pneumonia, strep throat, tuberculosis

True bacteria and disease• Bacteria involved in

diseases of plants, animals and humans, and in losses of food

Human Relevance of the Unpigmented, Purple, and Green Sulfur Bacteria

True bacteria and disease cont’d.• Modes of access of disease bacteria cont’d.

−Contamination of food and drink Food poisoning and diseases associated with

natural disasters»Cholera, dysentery, Staphylococcus and

Salmonella food poisoning Legionnaire disease Botulism Escherichia coli

Human Relevance of the Unpigmented, Purple, and Green Sulfur Bacteria

True bacteria and disease cont’d.• Modes of access of disease bacteria cont’d.

−Direct contact - enter through skin or mucus membranes Syphilis, Gonorrhea, anthrax, brucellosis

−Wounds Tetanus and gas gangrene

−Bites of insects and other organisms Bubonic plague, tularemia, rickettsias,

mycoplasmas, Lyme disease

Human Relevance of the Unpigmented, Purple, and Green Sulfur Bacteria

Koch’s Postulates - rules for proving particular microorganism cause of particular disease• Microorganism must be present in all cases of disease• Microorganism must be isolated from victim in pure

culture• Microorganisms from pure culture must be able to

infect hosts• Microorganism must be isolated from experimentally-

infected host and grown in pure culture for comparison with original culture

Human Relevance of the Unpigmented, Purple, and Green Sulfur Bacteria

True bacteria useful to humans• Biological Control organisms

−Bacillus thuringiensis - effective against caterpillars and worms Multiplies in digestive

tract and paralyzes gut−Bacillus popilliae - effective

against Japanese beetle grubs

• Bioremediation - use of living organisms in cleanup of toxic waste and pollution

Affect of Bacillus thuringiensis on tomato hornworm

Human Relevance of the Unpigmented, Purple, and Green Sulfur Bacteria

True bacteria useful to humans cont’d.• Other useful bacteria

−Human health - Lactobacillus acidophilus Aids in digestion Used for elimination of yeast infections

−Dairy - buttermilk, sour cream, yogurt, cheese− Industrial - utilizes bacteria waste products

Solvents, explosives, ascorbic acid (vitamin C), citric acid

Class Cyanobacteriae – The Cyanobacteria (Blue-Green Bacteria)

Distinctions between cyanobacteria and traditional bacteria• Has chlorophyll a and O2 produced from

photosynthesis

• Contain phycobilins

• Can fix N2 and produce O2

Class Cyanobacteriae – The Cyanobacteria (Blue-Green Bacteria)

• Pools and ditches, particularly if polluted

• Fresh and marine water, but not acidic water (plankton)

• Waters of various temperatures - hot springs at Yellowstone National Park

• Often 1st photosynthetic organisms after volcanic eruption

• Symbiotic with other organisms

Distribution in diverse variety of habitats

– Amoebae, sea anemones, lichens, cycadsYellowstone

Class Cyanobacteriae – The Cyanobacteria (Blue-Green Bacteria)

Form, metabolism, and reproduction• Often chains, or colonies

held together by gelatinous sheaths

• Cells blue-green in color in ca. 50% of approximately 1,500 spp.

• Produce nitrogenous food reserve - cyanophycin

• Flagella unknown

Class Cyanobacteriae – The Cyanobacteria (Blue-Green Bacteria)

Form, metabolism, and reproduction cont’d.• New cells by fission or

fragmentation of colonies or filaments

• Heterocyst - large colorless, N2-fixing cell

• Akinetes - thick-walled cells that resist adverse conditions

Class Cyanobacteriae – The Cyanobacteria (Blue-Green Bacteria)

Cyanobacteria, chloroplasts, and O2

• Chloroplasts originated as cyanobacteria or prochlorobacteria living within other cells

• Fossils of cyanobacteria, 3.5 bya, found in Australia• 3 bya, cyanobacteria produced O2 as by-product of

photosynthesis• O2 accumulated in atmosphere, becoming substantial

1 bya• Accumulation of O2 resulted in appearance of other

photosynthetic organisms and forms of aerobic respiration

• In last half billion years enough ozone for UV shield and for photosynthetic organisms to survive on land

Class Cyanobacteriae – The Cyanobacteria (Blue-Green Bacteria)

Human relevance of the cyanobacteria• Among many aquatic and photosynthetic organisms at

bottom of various food chains• Often abundant in bodies of fresh water in warmer

months−Algal Blooms - can be poisonous to livestock

• Food - Spirulina with significant vitamin content• Swimmers itch• N2 fixation

Class Prochlorobacteriae – The Prochlorobacteria

Have chlorophylls a and b, but no phycobilins• Adds to theory that

chloroplasts originated from cells living within cells of other organisms

Cell structure and chemistry similar to cyanobacteria and other true bacteria

Prochloron

Kingdom Archaea (Domain Archaea) – The Archaebacteria

Metabolism fundamentally different from other lines of bacteria

Differ from true bacteria by unique sequences of bases in RNA, by lack of muramic acid in walls, and by production of distinct lipids

Methane Bacteria• Killed by O2

• Active only under anaerobic conditions−Energy from generation of CH4 from CO2 and

H2

Kingdom Archaea (Domain Archaea) – The Archaebacteria

Salt Bacteria• Metabolism enables to

thrive under extreme salinity−Carry out simple

photosynthesis with aid of bacterial rhodopsin

Lake Bonneville, Utah with very high salt

content

Kingdom Archaea (Domain Archaea) – The Archaebacteria

Sulfolobus Bacteria• Occur in sulfur hot springs

• Metabolism allows to thrive at very high temperatures−Mostly in vicinity of 80oC (170oF), some even

higher

• Shape of ribosomes and chemistry of sulfolobus bacteria distinguishes them from other archaebacteria, true bacteria and eukaryotes

Kingdom Archaea (Domain Archaea) – The Archaebacteria

Human relevance of the archaebacteria• CH4 bacteria produce CH4 as they digest organic

wastes in absence of O2

−May be used to furnish energy for engines, heating and cooking

−Has high octane level and clean and nonpolluting−Produced on large-scale when organic wastes fed

into CH4 digester Leftover sludge makes excellent fertilizer

Viruses

• Size and structure:• Represent interface between biochemistry and life

−Lack cytoplasm or cellular structure−Don’t grow by increasing

in size or dividing−Don’t respond to external

stimuli−Can’t move on their own−Can’t carry on

independent metabolism −Express their genes and

produce more virus particles using host cell

• About size of large molecules, 15-300 nm

Papavoviruses in a human wart

Viruses

Size and structure cont’d.• Consist of nucleic acid core

surrounded by protein coat• Architecture of protein coat

varies−20-sided, or head and tail

• Core consists of DNA or RNA, not both

• Classified according to DNA or RNA, then according to size and shape, nature of protein coats, and # of identical structural units in cores

• Bacteriophages - viruses that attack bacteriaBacteriophage

Viruses Viral reproduction• Viruses replicate at expense of

host cells−Attach to susceptible cell−Penetrate to cell interior−DNA or RNA dictates

synthesis of new molecules−New viruses released from

host cell Host cell dies

• Some can mutate very rapidly– As result, new vaccines

need to be developedBacteriophage replication

Viruses Human relevance of viruses• Annual loss in work time due to common cold and

influenza viruses amount to millions of hours− Immunizations dramatically decreased incidence of

many viral diseases (i.e., chicken pox, German measles, and mumps)

• AIDS−Retrovirus - virus with 2 identical nuclear strands

Evolves extremely quickly»~1 million times faster than cellular

organisms• Used to infect disease organisms of animals and plants

−Ticks, insects, possibly gypsy moths

Viroids and Prions

Viroids - circular strands of RNA that occur in nuclei of infected plant cells• Transmitted from plant to plant via pollen,

ovules, or machinery−Cause more than dozen plant diseases

Prions - appear to be particles of protein that cause diseases of animals and humans• Believed to cause disease by inducing

abnormal folding of proteins in brain, resulting in brain damage−Cruetzfeldt-Jacob disease

Review

Introduction Features of Kingdoms (Domains) Bacteria and Archaea Domain Bacteria (Kingdom Bacteria) – The True Bacteria Human Relevance of the Unpigmented Purple, and Green

Sulfur Bacteria Class Cyanobacteriae – The Cyanobacteria (Blue-Green

Bacteria) Class Prochlorobacteriae – The Prochlorobacteria Kingdom Archaea (Domain Archaea) – The

Archaebacteria Viruses Viroids and Prions