Biotechnological applications of purple non sulphur phototrophic bacteria: A minireview.

ABSTRACT

Bacteria play in vital role in the production of variety of products, including certain plastics and enzymes used in detergents, textiles and pharmaceutical industries. Production of chemicals using bacteria and other microorganisms is not only economical sustainable but also ecofriendly. Modern biotechnology entails the use of cell fusion, bioinformatics, genetic engineering, structure based molecular design and hybridoma technology. The presence of photosynthetic bacteria along with the heterotrophic bacteria have been reported in various aquatic environments like Indian tropical waters (Vasavi et al., 2007), salt marshes (Bergstein et al., 1993), industrial effluents (Ramasamy et al., 1990; Merugu et al., 2008), sea water (Kobayashi,1982), sewage (Kobayashi et al., 1995), waste water (Sunita and Mitra, 1993 and Vasavi et al., 2007), hot water springs (Demchick et al., 1990), earthworm casts (Vasavi et al., 2007), paddy fields (Sasikala et al., 2004), ocean waters and aquaculture (Kappler et al.,2005), brackish lagoon (Anthony et al., 2006), and black sea (Overmann and Manske, 2006). Blankenship et al. (1995) studied taxonomy of anoxygenic photosynthetic bacteria. These bacteria preferably grow by a photoheterotrophic metabolism with organic substances as electron donors during their photosynthetic activity. Most species are also capable of growing photoautotrophically with molecular hydrogen as donor. They have high protein content with good amount of essential amino acids, vitamins, biological co-factors and fewer amounts of nucleic acids (Sasikala and Ramana, 1995, Merugu et al.,2008). Many workers have recommended purple non sulphur bacteria as a source of SCP for pisciculture and poultry industry (Salma et al., 2007), vitamin B12 (Sasikala and Ramana,1995), Ubiquinone Q10 used in clinical medicine (Sasaki et al., 2002) and therapeutically used compounds (Nagumo et al., 1991). Mitsui (1985), while discussing multiple utilisation of tropical and subtropical marine photosynthetic organisms, suggested that some photosynthetic bacterial strains may prove to be an economical source of carbohydrate material for bacterial mediated methane production. Carotenoids produced by Rb.sphaeroides are used as natural dyes and food dyes (Qian et al., 1991). The profile of essential amino acids of anoxygenic phototrophic bacteria is comparable to those of soyabean and egg proteins (Ponsanio et al., 2002) and higher than those of other single cell protein (Azad et al., 2001). Mass production of Rhodopseudomonas palustris as diet for aquaculture was studied by Kim and Lee (2000). Many of phototrophic bacteria are reported to leach out ammonia during their growth as amino acids. Ammonia leaching was observed in resting cells of Rhodobacter sphaeroides O.U.001 in the absence of MSX under various gas phases (Sasikala and Ramana, 1990). Hiroo (2004) used a mixed culture of photosynthetic bacteria for ammonia leaching.