Saran's Learn Microbiology

  Helicobacteria ·        Heliobacteria are Gram-positive, endospore-forming, anoxygenic phototrophic bacteria found in anaerobic soils and paddy fields. ·        Example – Heliobacterium chlorum , Heliobacillus mobilis , Heliospirillum photoanaerobium and Heliomicrobium modesticaldum . ·        Number of Species – There are over 40 validated species within the Helicobacter genus, with new species occasionally being discovered in different animal hosts. ·        Habitat – Soil, paddy fields, hot springs, alkaline soils, anaerobic mud, soda lakes; commonly found in waterlogged agricultural fields (especially rice field). ·        Mode of Nutrition – Photoheterotrophic, require organic carbon sources and use light as an energy source. ·        Mode of Reproduction – Reproduce asexually via Binary fis...

Green Non-Sulfur Bacteria ·        Example – Chloroflexus aurantiacus , Chloronema giganteum , Oscillochloris trichoides and Herpetosiphon aurantiacus. ·        Number of Species – Around 30 – 35 species. ·        Habitat – Hot springs, alkaline springs, marine sediments, microbial mats, geothermal areas; thrive in hot, low-oxygen, illuminated environments. ·        Mode of Nutrition ü   Photoheterotrophy (Primary Mode): They preferentially use light for energy but require organic compounds (e.g., sugars, amino acids, organic acids) as carbon sources. ü   Photoautotrophy (Alternative Mode): Some, like Chloroflexus, can fix CO ₂ , but they use a unique pathway called the 3-Hydroxypropionate pathway, which is different from the Calvin cycle (used by plants and purple bacteria) and the rTCA cycle (used by green sulfur bacteria). ü   Chemoheterotrophy:...

  Green Sulfur Bacteria ·        Example – Chlorobium limicola , Chlorobaculum tepidum , Prosthecochloris aestuarii and Pelodictyon luteolum. ·        Number of Species – Over 90 species, found mainly in the family Chlorobiaceae. ·        Habitat ü   Anaerobic zones of lakes and ponds, sulfur-rich environments, stagnant waters, sulfur springs, marine sediments. ü   Live in deep, low-light zones where H ₂ S is abundant. ·        Mode of Nutrition – Obligate photoautotrophs ( use light as energy and CO ₂ as carbon source). ·        Mode of Reproduction – Binary fission (Asexual mode) ·        Mode of Respiration – Obligate anaerobes (cannot survive in presence of oxygen). ·        Type of Photosynthesis – Anoxygenic photosynthesis (do not use water as an elect...

  Purple Non-Sulfur Bacteria ·        Example – Rhodospirillum rubrum , Rhodobacter sphaeroides , Rhodopseudomonas palustris and Rhodomicrobium vannielii ·        Number of Species – There are over 100 described species across multiple genera, and new species are still being discovered and characterized thanks to modern genetic techniques. ·        Habitat – Anoxic environments such as freshwater, marine sediments, paddy soils, and wastewater, and can persist in both aquatic and terrestrial settings even when environmental conditions fluctuate. ·        Mode of Nutrition ü   Photoheterotrophs, using light for energy and organic compounds as carbon sources. ü   Photoautotrophy (using CO ₂ as a carbon source). ü   Chemoheterotrophy (respiring organic matter in the dark). ü   Mixotrophy depending on light and oxygen availability. · ...