LECTURE 13. THE BACTERIA (cont.) Photosynthetic Bacteria, phylogenetically widespread. And many Proteobacteria. Photosynthetic Bacteria

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1 Photosynthetic Bacteria, phylogenetically widespread LECTURE 13 THE BACTERIA (cont.) And many Proteobacteria Photosynthetic Bacteria > Green Sulfur > Green Nonsulfur > Purple Sulfur > Purple Nonsulfur Anoxygenic Photosynthesis > Green Sulfur - Chlorobi > Green Nonsulfur - Chloroflexi > Purple Sulfur Proteobacteria > Purple Nonsulfur > Cyanobacteria Oxygenic Photosynthesis New terms with relation to the cyanobacteria: 1) Trichome = row of bacterial cells in a filament. 2) Akinetes = specialized dormant cells that are very resistant to desiccation. Oscillatoria

2 3) Heterocysts = special cells where nitrogen fixation takes place. Photosystem I still makes ATP, but get rid of PS II, so no O2 is made. The O2 would poison the enzyme that fixes the nitrogen, nitrogenase. The heterocyst gets nutrients from nearby vegetative cells and gives them the fixed nitrogen that it makes. Other tidbits about cyanobacteria: > Many disperse via gliding motility > Common in almost all waters and soils. > They are the algae half of most lichens, and many others are symbiotic with other organisms. The Chlamydiae and Planctomyces

3 The Chlamydiae obligate intracellular parasites - can t make their own ATP! very small in size - and no peptidoglycan thus not sensitive to penicillin. genus Chlamydia (many human pathogens) Trachoma and genetical chlamydial infections are caused by different strains of C. trachomatis Fig C. trachomatis attaching to fallopian tube mucosal cells Fig Numbers indicate development of infectious elementary bodies. Elementary bodies - infectious spores Reticulate bodies - growing cells inside vacuoles of host cells Planctomyces - large group of aquatic bacteria related to Chlamydia, but none cause disease. Most have never been grown in the lab The Spirochaetes - No peptidoglycan - cell walls are protein (= S-layer). - Reproduce by budding - Have stalks made of protein (no cytoplasm inside). - All have internal compartments.. e.g. see nucleoid of Gemmata or anammoxosome of Brocadia The Spirochaetes Fig > have flexible, helical shape Spirochaetes live in diverse habitats Usually anaerobic (facultative or obligate) > Also distinguished by motility - can move through viscous solutions > Use unique structure called the axial filament Group contains some important pathogens, but most are harmless muck dwellers (or e.g. between your teeth)!treponema pallidum - Syphilis!Borrelia burgdorferi - Lyme Disease!Leptospira interrogans - an aerobic spirochaete! leptospirosis (kidney infection)

4 Bacteroides/Flexibacter/Cytophaga (CFB group) Bacteroides anaerobic - hard to culture, some can be opportunistic pathogens important in rumens and colons - Bacteroides = dominant genus in the colon - 10 billion per gram of human feces break down polymeric substrates (e.g. cellulose) using extracellular enzymes - use gliding motility Cytophaga and Sporocytophaga Obligate aerobes - most important aerobic, bacterial degraders of cellulose in the biosphere.. Extracellular cellulases - see overheads LECTURE 14 GRAM POSITIVE BACTERIA. GC content is useful for classifying Bacteria - especially Gram + % G + C = (G + C)/(G + C + A + T) x 100 = percentage of guanine (G) and cytosine (C) in the DNA of the organism. Quick method to group organisms, but two organisms can have similar %G+C but completely different DNA sequences. It is only useful in conjunction with other tests and for groups that differ by > 10% or so in G+C.

5 Low G+C Gram Positives The Mycoplasmas Clostridia Bacilli Lactic Acid Bacteria The Mycoplasmas lack cell walls pleomorphic - very flexible because no cell walls The Clostridia - Clostridium obligately anaerobic endospore producers have smallest bacterial genomes (~500,000 BPs) about 1/8 the size of E. coli most are parasites or commensals Fig Colonies of Mycoplasma pneumoniae. Some pathogens: C. tetani - causative agent of tetanus spoil food, even canned foods - food borne pathogens: C. botulinum and C. perfringens Boiling (100 C) won t kill them; autoclaves or pressure cookers needed to kill endospores (121 C for 20 min.) Clostridium can ferment amino acids remember the Stickland reaction. The Clostridia - Heliobacteria One amino acid is oxidized another is the electron acceptor to restore NAD +. photosynthetic bacteriochlorophyll g some will form endospores

6 The genus Bacillus endospore formers chemoheterotrophs usually motile usually rapid growers Fig a. Bacillus anthracis spores form in middle of cells. b. Clostridium tetani spores at the end of cells. Important Bacillus species: B. anthracis - causitive agent of anthrax Organisms studied by Koch - important agricultural pathogen. Mail tainted with anthrax spores found recently. diverse group - likely to be split into at least 5 groups WWII, Brits experimented with B. anthracis on Gruinard island off Scotland. Sheep were placed in pens and bombs filled with anthrax spores were dropped on the island. The sheep started dying 3 days later. The island had to be quarantined for 48 years. In 1987, they soaked the island with 280 tons of formaldehyde in 2800 tons of seawater then removed the topsoil - the island was declared safe in 1990, but there are still few visitors. Bacillus thuringiensis - Bt B. sphaericus Both species form a parasporal body - a solid protein crystal next to their spores. These species of bacteria kill insects: B. thuringiensis - moth larvae (caterpillars) - beetle larvae B. sphaericus - mosquito larvae Genes from Bt have been integrated into several plant genomes to give plants permanent resistance to pests: