Helicobacteria

 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 fission.

·       Mode of Respiration – Obligate anaerobes.

·       Type of Photosynthesis – Anoxygenic photosynthesis.

·       Pigments – Bacteriochlorophyll g (unique pigment found only in Heliobacteria) and Carotenoids.

·       Electron Donor – Organic compounds, sometimes H₂; not water, which is why no oxygen is produced.

·       By-products – Fermentation by-products can include organic acids and, in some conditions, small amounts of hydrogen gas.

·       Photosystem – Photosystem I–type reaction center only.

·       Ecological role

ü  Nitrogen fixation (important in rice-field ecosystems).

ü  Contribute to carbon cycling in anaerobic soils.

ü  Survive harsh conditions due to endospore formation.

ü  Support microbial communities in mud and sediments.