Chapter 11

The Prokaryotes:Domains Bacteria and Archaea

Firmicutes Actinobacteria

Domain Bacteria

• Prokaryotes• Single cell organisms• Circular chromosome• Peptidoglycan cell wall• Binary division

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Types of Diversity• Morphological diversity:

– Bacilli, cocci, and spirals are 3 common shapes– Filamentous forms, pleiomorphic forms. – There are many varieties of size, ranging from submicroscopic up to a few

bacteria that can be seen with the naked eye. • Structural diversity:

– Cell wall• Gram-positive and gram-negative bacteria.• Absence of walls

– External appendages – Endospores

• Metabolic diversity: – Heterotrophs vs autotrophs.– Fermentation vs respiration. – Aerobic and anaerobic.– Photosynthesis

• Genetic diversity: – Small ribosomal subunit sequencing – 16S r RNA

Detailed phylogenetic tree of the major lineages (phyla) of Bacteria based on 16S ribosomal RNA sequence comparisons

Firmicutes Actinobacteria

Prokaryotes

Phylum PhylumFirmicutes Actinobacteria

Phylum Firmicutes• Gram-positive

• Low G + C (less than 60%)

• Very popular is the plasmid exchange across species and genera of this phyla.

Orders:

Phylum Firmicutes• Rods:

– Genus Bacillus• Aerobic and facultative anaerobic• Endospore forming rods• Common in soil• Human and animal disease – anthrax, food poisoning

– Genus Clostridium• Obligate anaerobes• Endospore forming rods• Toxin produced• Human pathogens – tetanus, botulism, gangrene, diarrhea

– Genus Lactobacillus• Generally aerotolerant anaerobes, lack an electron-transport chain• Lactic acid fermentation of carbohydrates• Used for yogurt, buttermilk, pickles, sauerkraut• Live on human mucous – oral cavity, vagina, intestine

– Genus Listeria• Can grow at 4°C• Contaminant of meat and dairy• Survive phagocytosis• Cross placenta cause fetus damages

Phylum Firmicutes• Coccus

– Genus Staphylococcus• Coci in clusters• Tolerate high osmotic pressure• Live on human skin and nose• Human disease – food poisoning, toxic shock

syndrome – Genus Streptococcus

• Coci in chain• Produce tissue and cell digesting enzymes and toxins • Avoid phagocytosis• Human disease – pharyngitis, dental caries, scarlet

fever, impetigo, rheumatic fever, neonatal sepsis – Genus Enterococcus

• Live on human mucous - oral cavity, vagina, intestine• Antibiotic resistant• Human disease – nosocomial infections, surgical

wounds, urinary tract infections• Genus Mycoplasma

– No cell wall, sterols in membrane, pleomorphic– 0.1 - 0.24 µm– Can grow in filamentous form or single– Human disease - pneumonia M. pneumoniae

Phylum Actinobacteria

• Gram-positive - High G + C (more than 60%)– Coccoid, rod-coccoid , fragmenting hyphal forms, filamentous with

permanent and highly differentiated branched mycelium

– Physiologically very diverse • production of numerous extracellular enzymes, including antibiotics

Phylum Actinobacteria• Genus Mycobacterium

– usually bacilli, slow growth– cell wall has mycolic acid (acid fast) – human diseases: leprosy and tuberculosis

• Genus Propionibacterium– rod shape, form propionic acid– on human skin, cause acne.

• Genus Cornebacterium– rods, pleomorphic– human disease: diphtheria

• Genus Streptomyces– aerobes, filamentous, common in soil– produce external asexual spores– produce many antibiotics

• Genus Actinomyces– facultative anaerobes, filamentous,– in human oral mucous– human disease: actinomycosis

• Genus Nocardia– aerobes, filamentous, reproduce by fragmentation– acid fast, – in soil– human disease: pulmonary infections, mycetoma

Phylum CyanobacteriaPhylum Spirochetes Phylum ChlamydiaePhylum Bacteroidetes Phylum Fusobacteria

Phylum Proteobacteria

Class (alpha) Class (beta) Class (gamma) Class (delta) Class (epsilon)

• Mythical Greek god, Proteus, who could assume many shapes

• Proteobacteria is the largest group of bacteria.

• This phylum contains 2086 species or 32.3% of all known bacteria.

• Proteobacteria are all gram negative.

• All four of major nutrition types are present – Purple phototrophic.

– Nitrifying bacteria

– Enteric bacteria

– Bacteria responsible for animal bioluminescence.

• Many pathogens.

• More morphologically unusual bacteria.

• Symbiotic genera.

Phylum Proteobacteria

Class (alpha) Proteobacteria• Obligate pathogen

– Genus Rikettsia• Induce phagocytosis and multiplies in phagocytes• Transmitted via flea and tick bites• Human disease – spotted fever: typhus, Rocky Mountain – damage the permeability of blood capillaries.

– Genus Ehrlichia• Lives in white blood cells- phagocytes• Transmitted via tick bite• Human disease ehrlichiosis

• Human pathogens– Genus Bartonella

• Transmitted via cat saliva• Human disease – cat-scratch disease

– Genus Brucella• Survives phagocytosis• Human disease brucellosis

• Plant pathogens– Genus, Bradyrhizobium, Agrobacterium

• Industrially important– Genus Acetobacter, Glaunobacter

• Convert ethanol to acetic acid

• Nitrogen fixation – Genus Rhizobium, Azospirilum

• Grow on roots

The (beta) Proteobacteria• Genus Spirillum

– spiral, motile: polar flagella– in fresh water– human disease: rat bite fever– transmitted via rodent bite or fecal

contamination• Genus Burkholderia

– motile: single polar flagellum– Diverse carbon source– grow in disinfectants– human disease: respiratory infections

• Genus Bordetella– human pathogen– whooping cough/pertussis

• Genus Neisseria– on mucus membranes of mammals– human pathogen– Gonorrhoea, meningitis

• Genus Zoogloea– aerobic sewage treatment– form precipitating flocs

• Genus Pseudomonas– Opportunistic pathogens

– Metabolically diverse

– Motile -polar flagella

– Produce water soluble blue pigment

– Can live on soap, adhesives, antiseptics

– Can grow at 4°C: food spoilage

– Antibiotic resistant

– Wound infections, infections in immunocompromized patients

• Genus Vibrio: – curved rod,

– Found in coastal water• Vibrio cholerae causes cholera

• Genus Legionella– Live in fresh water

– Contaminant of AC ducts

– Human disease – Legionnaire’s disease

• Genus Azotobacter and Azomonas

– Nitrogen fixing

Class (gamma) Proteobacteria

Figure 11.7

– Order Enterobacteriales • facultative anaerobes, ferment carbohydrates• Peritrichous flagella, • Have fimbriae and Sex pili• Produce bacteriocins• Human pathogens, most cause gastrointestinal, urinary or respiratory tract

infections– Escherichia

» Normal microbiota, can cause gastroenteritis, UTIs– Salmonella

» Common animal microbiota» Toxin cause salmonellosis

– Shigella» Toxin cause shigellosis

– Enterobacter» In soil, water, animals and humans, can cause nosocomial and UTIs

– Klebsiella» In soil and water, can fix nitrogen, can cause pneumonia

– Proteus» Swarming growth, wound infections

– Serratia» Red pigment , can cause respiratory and UTIs

– Yersinia» Black Death plaque, transmitted via fleas from rats and ground squirrels

– Erwinia» Plant pathogen – hydrolyze pectin: plant rot

Class (gamma) Proteobacteria

Class (delta) Proteobacteria

• Include some bacteria that have predators on other bacteria

• Important contribution to sulfur cycle.

• Genus Bdellovibrio– motile: single polar flagella

– attacks other Gram negative bacteria

– reproduces in periplasm

• Genus Myxococcus– motile via slime trails

– digest bacteria

– low nutrients: aggregate to form a fruiting body ! myxospores

• Slender gram-negative rods that are curved to spirilloid

• Flagella – one polar flagellum or multiple flagella

• Pathogens - peptic ulcers, stomach - flagellated

• Unicellular to multicultural filamentous and colonial type

• Genus Campylobacter– animal disease: spontaneous abortion

– human disease: food borne intestinal disease

• Genus Helicobacter– human disease: peptic ulcers

Class (epsilon) Proteobacteria

Purple and Green Photosynthetic Bacteria• Oxygenic and Anoxygenic photosynthesis

2H2O + CO2

light

(CH2O) + H2O + O2

2H2S + CO2

light

(CH2O) + H2O + 2S

• The only bacteria that carry out oxygenic photosynthesis

• Some growth in associations with plants and animals

• CO2 fixation, Fix nitrogen

• Gliding motility

• The chloroplasts found in all photosynthesized organisms evolved from this group of bacteria

Phylum Cyanobacteria

Phylum Spirochetes• Coiled morphology

• Axial filament-enclosed in the space between the outer sheath and the body of the cell

• Number of important pathogenic bacteria

– Treponema – syphilis

– Borrelia – lyme disease, transmitted via tick from mice

– Leptospira – leptospirosis, transmitted via animal urine contaminated water

• No peptidoglycan• Divide in animal cell• Produce spore-like elementary bodies

– C. trachomatis• Trachoma• Urethritis• Pelvic inflammatory disease

– C. pneumoniae• Pneumonia

– C. psittaci • Causes psittacosis

Phylum Chlamydiae

Figure 11.23

Bacteroidetes and Fusobacteria• Phylum Bacteroidetes

– Anaerobic

• In mouth and large intestine

• Cellulose-degrading in soil

– Genus Bacteroides

• In human and animal GIT, can infect puncture wound and peritoneum

– Genus Cytophaga

• In soil, degrade cellulose

• Phylum Fusobacteria– Fusobacterium

• Found in mouth

• Anaerobic

• May be involved in dental diseases

Domain Archaea

• Cell wall - No peptidoglycan

• Unusual metabolism that allow them to live in the most inhospitable places on Earth (extreme environments)– Oxygen-free habitats – Boiling sulfuric acid pools near volcanoes – Sulfur hot springs – Glacial ice – Methane seeps – Desert sands – Acid mines – Oil leaks – Polluted waters – Toxic waste dumps

Detailed phylogenetic tree of the Archaea based on 16S ribosomal RNA sequence comparisons.

Domain Archaea• Korarchaeota;

– Found only in high temperature hydrothermal environments (hot springs). – None have been grown in pure culture.

• Crenarchaeota: – They use sulfur compounds as electron donors or as acceptors. – Most thermophilic organisms known. – Significant in deep-sea environment and as wall as in polar seas

• Euryarchaeota: – Methanogens - microorganisms that produce methane as a metabolic byproduct in anoxic

conditions – Halophiles - extremophile organisms that live in environments with very high concentrations of

salt. ("salt-loving“). – Thermophiles

• Nanoarhaeota – recently discovered smallest organism, nanosized, hyperthermophilic symbiont.

• Bacteria size range– Thiomargarita (750 µm)

– Nanoarhaeota (0.4 µm)

• PCR indicates up to 10,000 bacteria/g of soil.

• Many bacteria have not been identified or characterized because they haven't been cultured– Need to be cultured to understand their metabolism and ecological role

• Need special nutrients

• Are part of complex food chains requiring the products of other bacteria

Microbial Diversity

Figure 11.26

Learning objectives

• Distinguish among the alpha proteobacteria .

• Distinguish among the beta proteobacteria.

• Distinguish among the orders of gamma proteobacteria .

• Distinguish among the delta proteobacteria.

• Distinguish among the epsilon proteobacteria.

• Compare and contrast the green and purple photosynthetic bacteria with the cyanobacteria.

• Distinguish among the low G + C gram-positive bacteria.

• Distinguish among the high G + C gram-positive bacteria.

• Distinguish among the gram-negative nonproteobacteria.

• Distinguish, spirochetes, Bacteroidetes, and Fusobacteria.