Lecture 4.14 Notes

Lecture 4.14 Notes - Notes Actinobacteria Mycobacterium...

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Notes - 4/14/10 Actinobacteria: Mycobacterium Most species have relatively simple nutritional requirements o w/ exception of M. leprae , which has never been successfully cultured o Two major groups: fast and slow growers Acid-fast rods: due to mycolic acids o Mycolic acids covalently attached to peptidoglycan waxy hydrophobic cell surface o Alkali and phenol resistance basis of enrichment procedures (sputum treated w/1M NaOH prior to plating) Pleomorphic morphology – may be filamentous or branching Pathogenicity of M. tuberculosis correlated with formation of chordlike structures chord factor expression on cell surface Filamentous actinobacteria: Streptomyces and relatives Filamentous Gram-positives found primarily in soil o Geosmins: sesquiterpenoid compounds produced by Streptomyces (and some cyanobacteria) earthy odor of soil > 500 species of Streptomyces recognized formation of mycelia analogous to filamentous fungi development of spores: conidia o much simpler development than endospores classification includes morphologies of spore-bearing structures, which may be pigmented Important source of antibiotics: > 500 distinct antibiotics known and many more suspected; o >60 used in human and veterinary medicine o antibiotic production may be mechanism to allow Streptomyces to complete sporulation process in limiting nutrient conditions CYANOBACTERIA One of the major phyla of Bacteria Large and morphologically heterogeneous group of phototrophic Bacteria Major milestone with evolution of oxygenic photosynthesis 2.8 billion years ago Characteristic photosynthetic reaction centers incorporating chlorophyll a and phycobiliproteins
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Five major groupings of multiple genera with distinct phenotypic and morphological properties Complex and multilayered photosynthetic membrane systems of cyanobacteria Only one form of chlorophyll - chlorophyll a All species also synthesize characteristic biliprotein pigments: phycobilins. These are light harvesting proteins that increase the efficiency of light delivery to the photosynthetic reaction centers. Phycobiliproteins absorb lower wavelength light and transfer it to the reaction center where it is absorbed by longer-wavelength-absorbing chlorophyll a Many cyanobacteria also synthesize gas vesicles so that cells can reside in regions of optimal light intensity Phycobilins : open chain tetrapyrrole derived biosynthetically from a closed porphyrin ring Phycocyanin: blue pigment that gives species producing it their
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Lecture 4.14 Notes - Notes Actinobacteria Mycobacterium...

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