Prokaryotes (Bacteria and Archaea)

What are deeply branching bacteria? *

• closest living relatives of the earliest living things on Earth

• Live in habitats similar to early Earth (Anaerobic to Microaerophilic, + Thermophilic)

• Examples = Aquifex and Deinococcus bacterium

• Autotrophic + not pathogenic

What are Gram-Negative ProteoBacteria?

• Largest + most diverse group of bacteria

• Arose from common photosynthetic ancestor

• Phylogenetic relationship is based on rRNA studies

• Classes of gram-negative proteobacteria include:

  - Alphaproteobacteria

  - Betaproteobacteria

  - Gammaproteobacteria

  - Deltaproteobacteria

  - Epsilonproteobacteria

What are Alphaproteobacteria?

• Class of gram-negative bacteria that can grow in low nutrient conditions

• Some have protrusions known as prosthecae*

  • Stalks or buds

• Important! Includes bacteria capable of nitrogen fixation.

  • Important for plants and animals (us)

What are Non-proteobacteria gram-negative bacteria? *

• These are phototrophic bacteria

  • Have photosynthetic lamellae

  • 5 bacteria types based on pigments + source of electrons

    • Blue-green (Cyanobacteria)

    • Green sulfur

    • Green non sulfur

    • Purple sulfur

    • Purple non sulfur

Other Gram-Negative Bacteria *

• Phylum - Chlamydiae

  • Genus: Chlamydia*

• Do NOT contain peptidoglycan in their cell walls

• Human-to-human transfer

• Obligate intracellular parasites

• Causes -

  • Chlamydia trachomatis

  • Pneumonia

  • STI’s

Azospirillium

• Soil microorganisms associated w/ roots

  • Tropical grasses + sugar cane

• Symbiotic relationship w/ plants! Mutualism

  • Fixes nitrogen from the atmosphere usable for plants

  • Plant provides nutrients for the microorganism

Rhizobium *

• Agriculturally important - Infect the roots of legumes, rhizobia

• Causes formation of nodules on roots

• Mutualism + fixes nitrogen

• Grows inside cortical cells, creating the nodules

Agrobacterium *

• Plant pathogen

• Uses horizontal gene transfer causing tumors/gall

  • Contain plasmids that randomly integrate into the plant’s genome

• Agrobacterium tumefaciens - causes Crown gall disease

Nitrobacter and Nitrosomes

• Free-living, nitrifying bacteria + in soil

• Chemoautotrophs

• Crucial to the nitrogen cycle

• NO(3) can be used by plants and is better than NH(3)

  • Motile in soil, easily absorbed, synergistically promotes the uptake of other cations

Rickettsia *

• Coccobacilli

• Obligate intracellular parasite

  • Only reproduce in mammalian cells

• Transmit to humans by insect bites

• Enters by phagocytosis, multiplies quickly in host cell

• R. rickettsii - causes Rocky mountain spotted fever (ticks = vector)

  • can lead to amputation, hearing loss, mental disability, 20-30% fatality w/ no antibiotics

Caulobacter *

• Found in low nutrient environments - lakes

• Have stalks that anchors it to surfaces

  • Helps catch nutrients in continuous flowing water

• Divide by budding

Pseudomonas *

• Aerobic, rod-shaped, and moves w/ polar flagella

• Very large genomes

• Forms fluorescent pigments

• Common in soil - decomposition of uncommon chemicals like pesticides

• Opportunistic pathogen - causes disease in a weakened host, UTI, and wounds

• Produce a variety of enzymes, allowing them to grow on small traces of unusual carbons

  • grows on soaps + antiseptics

• Resistant to antibiotics

  • Porins in the cell wall won’t allow antibiotics in

  • Efflux pumps eject antibiotics away

Legionella *

• Intracellular pathogens

  • require a mammalian host to reproduce

• Legionella - Found naturally in streams (can infect water supplies)

  • Can survive + reproduce in aquatic amoebas = hard to eradicate

  • Causes legionnaires disease (pneumonia)

  • NOT transferable person-to-person

Enterobacteriaceae (Enterics) *

• Large family of gram-negative bacteria

• Facultative anaerobes, rods, if mobile it is peritrichously (all over) flagellated

• Called Enterics - found in intestinal tracts

• Active fermenters of glucose + other carbohydrates

• Fimbrae helps adhere to surfaces, pili - exchange genetic info

Examples of Enterics (7)

• Escherichia -

  • Most numerous inhabitant of our gut

  • Important to science and biotechnology

  • Indicator of fecal contamination in water

  • Not usually pathogenic, E.coli 0157 = serious food poisoning

• Salmonella -

  • All members of the genus are potentially pathogenic

  • Causes Salmonellosis

• Shigella -

  • Shigellosis: Life-threatening, bloody diarrhea w/ fever and cramps. Toxins produced.

• Klebsiella -

  • Found in soil + water

  • Many islets can fix nitrogen

  • Occasionally causes serious pneumonia

• Yersinia -

  • Yersinia pestis: Bubonic plague

  • Ground squirrels in southwest

  • Fleas on animals → humans

• Proteus -

  • Swarm on agar plates

  • Causes UTI in patients w/long-term catheterization

• Serratia -

  • Produces red pigment at 25 degrees Celsius

  • Found in catheters & irrigation solutions (Urinary + respiratory tract infections)

Bdellovibrio (genus) *

• Attaches and penetrates the membrane of other gram-negative bacteria and reproduces in the periplasm

Myxobacteria (group) *

• Vegetative cells glide and leave a slime trail

• Digest bacteria they encounter

• Form a mound in low-nutrient environments and then becomes a fruiting body that produces spores

Cyanobacteria (group) *

• Blue-green pigment

• Does photosynthesis

• Most can fix Nitrogen from the atmosphere

  • occurs in specialized cells called heterocysts

• Unicellular to colonial to filamentous

  • Their filamentous form exhibits cellular differentiation

Gram-Positive Bacteria (Low G + C) *

• DNA has lower % of Guanine and Cytosine, < 50%

• Phylum - Firmicutes

• Important for endospore formers

• Includes:

  • Clostridia* (21-54%)

  • Mycoplasma (23-40%)

  • Bacilli

    • Listeria

    • Lactobacillus

  • Cocci

    • Streptococcus*(33-44%)

    • Enterococcus

    • Staphylococcus*

Gram-Positive Bacteria (High G + C) *

• DNA contains high G + C content, > 60%

• Phylum - Actinobacteria

• High pleomorphic morphology

  • Alters shape + size in response to environmental conditions

• Includes:

  • Streptomyces* - branching filament growth (star-like colonies)

  • Mycobacterium* - TB and leprosy

Streptomyces

• Filamentous growth

• Aerobic, found in soil

• Have spores at the end of aerial filaments

• Produce most of our common antibiotics

  • Antibacterial, antifungal, antiparasitic

Spirochetes

• Coiled morphology

• Axial filaments: Corkscrew-like motility

• Found in the human oral cavity

• Associated diseases:

  • Treponema - Syphilis

  • Borrelia - Lyme disease

Mycobacterium

• Aerobic, non-spore-forming rods

• Distinctive cell wall

  • Acid fast

  • Drug resistance

  • Pathogenicity

• Causes:

  • M. tuberculosis

  • M. leprae

    • Skin sores, nerve damage, muscle weakness

Streptococcus

• Spherical, usually in chains

• Produce extracellular substances, contributing to pathogenesis

  • Enzymes that:

    • Destroy phagocytic cells

    • Digest connective tissue

    • Digest fibrin in blood clots

• Responsible for the most illnesses/diseases than any group

• Beta-hemolytic: Produce hemolysin that lyses blood cells forming clear zones on blood agar plates

  • S. pyogenes, “Group A Strep)

    • Scarlet fever

    • Sore throat

    • Rheumatic fever

  • S. agglactiae “Group B Strep)

    • Postpartum infections + neonatal sepsis

• Alpha-hemolytic:

  • Appears greenish hue on blood agar due to partial destruction of blood cells

  • S. pneumoniae -

    • Pneumococcal pneumonia

  • S. mutans -

    • Dental decay

Staphylococcus

• Cocci, “grape clusters”

• Grows in nasal passages + skin, normal microbiota

• S. aureus -

  • MRSA

  • Infection of wounds of surgical procedures

  • Production of toxins contributing to pathogenicity

  • Toxic shock syndrome

  • Becomes drug-resistant quickly

Archea

• Common features:

  • Lack of true peptidoglycan

  • Cell membranes have branched hydrocarbon chains

  • Start codon - methionine

• Reproduction: Binary fission or budding

• Cocci, bacilli, or spiral

• NOT disease causing

What are Extremophiles?

• Organisms that thrive in extreme environmental conditions

What are Methanogens?

• Anaerobic

• Convert CO2, H2, and organic acids into Methane (CH4)

• Convert organic wastes in ponds, lakes, and the ocean

Thermophiles

• DNA, RNA, cytoplasmic membranes, and proteins don’t function below 45 degrees Celsius

  • Found in hot springs, deep sea vents, etc.

Halophiles

• Thrive in high salt concentrations. Require > 9% NaCl to maintain cell wall integrity

• Found in -

  • Salted fish and hyper saline lakes

Acidophiles

• Grow in low pH

  • volcanic fields, sulfuric acid pools

Nitrogen Fixing Bacteria

• Azospirillium

• Nitrobacter

• Nitrosomes

• Rhizobium

• Klebsiella (enteric)

• Cyanobacteria

Clostridium (Clostridia)

• Obligate anaerobes

• Rod-shaped w/ endospores

  • Plays an important role in pathogenicity + food spoilage

• Diseases associated w/ clostridia

  • C. tetani

  • C. perfringens

  • C. botulinum

  • C. difficile

C. Tetani

• Tetanus

  • Infection characterized by muscle spasms

  • Contaminated objects

C. perfringens

• Normal in decaying vegetation and microbiota of animals, insects, and marine sediments

• Foodborne disease

• Gas gangrene - open wounds

C. botulinum

• Botulism - muscle weakness

• Floppy baby syndrome

  • C. botulinum spores in honey

C. difficile

• Diarrhea (C. diff)

• Wash hands w/ water