Ch. V. Ramana

Anoxygenic phototrophic bacteria: Physiology and advances in hydrogen production technology

Publisher Summary The chapter focuses on the physiological aspects regulating hydrogen metabolism in anoxygenic phototrophic bacteria, along with technical and economical aspects of hydrogen production, with particular reference to purple nonsulfur bacteria. Studies on the growth phase of the organism are considered equally important as studies on hydrogen production by resting cells; hence, the chapter explains in general the physiology related to hydrogen metabolism and other important related areas of research on anoxygenic phototrophic bacteria. Biological hydrogen evolution is still in an exploratory stage in bioenergy production research, unlike methane (biogas) and alcohol production. There is enough justification to carry out further work that now concentrates on process development rather than on strain selection. For this futuristic research, a multi- and interdisciplinary approach is the need of the day.

Environmental regulation for optimal biomass yield and photoproduction of hydrogen by Rhodobacter sphaeroides O.U. 001

The effect of pH, temperature, light intensity and concentration of carbon source/e− donor and nitrogen source on the regulation of biomass yield and photoproduction of hydrogen (the fuel of the future) by a purple non-sulfur photosynthetic bacterium, Rhodobacter sphaeroides O.U. 001, was studied. The importance of culture density and age on the hydrogen photoproduction is also discussed.

Degradation of chlorinated nitroaromatic compounds

Chlorinated nitroaromatic compounds (CNAs) are persistent environmental pollutants that have been introduced into the environment due to the anthropogenic activities. Bacteria that utilize CNAs as the sole sources of carbon and energy have been isolated from different contaminated and non-contaminated sites. Microbial metabolism of CNAs has been studied, and several metabolic pathways for degradation of CNAs have been proposed. Detoxification and biotransformation of CNAs have also been studied in various fungi, actinomycetes and bacteria. Several physicochemical methods have been used for treatment of wastewater containing CNAs; however, these methods are not suitable for in situ bioremediation. This review describes the current scenario of the degradation of CNAs.

Biotechnological Potentials of Anoxygenic Phototrophic Bacteria. I. Production of Single-Cell Protein, Vitamins, Ubiquinones, Hormones, and Enzymes and Use in Waste Treatment

Publisher Summary Biotechnology, which is being studied globally for possible practical exploitation, can provide economical and efficient solutions for the problems addressed in detail. The advantages of anoxygenic phototrophic bacteria include metabolic versatility which makes it possible to grow them by various growth modes including photo- and chemoautotrophy, heterotrophy, and fermentation, coupled to high growth rates and easy manipulation. The chapter explores that, as light is the source of energy, these bacteria can prove highly beneficial for industrial applications similar to those for which microalgae are already being used in the field of biotechnology and microbiology. In addition, the chapter also discusses the use in waste treatments. Apart from those uses discussed in this chapter, anoxygenic phototrophic bacteria can be used in the production of biopolyesters, fuel (hydrogen), insecticides, along with their potential use as biofertilizers.

Erythrobacter odishensis sp. nov. and Pontibacter odishensis sp. nov. isolated from dry soil of a solar saltern

Two bacterial strains (JC130(T) and JA747(T)) were isolated from dry soils of a solar saltern. Phylogenetic analysis showed that strain JA747(T) clustered with species of the genus Erythrobacter belonging to the family Erythrobacteraceae of the class Alphaproteobacteria in the phylum Proteobacteria, while strain JC130(T) clustered with species of the genus Pontibacter belonging to the family Cytophagaceae of the phylum Bacteroidetes. Based on 16S rRNA gene sequence analysis, strain JA747(T) had highest similarity with Erythrobacter gangjinensis K7-2(T) (96.7 %) and other members of the genus Erythrobacter (<96 %). Strain JC130(T) had highest sequence similarity with Pontibacter korlensis X14-1(T) (98.1 %), Pontibacter actiniarum KMM 6156(T) (96.9 %) and other members of the genus Pontibacter (<96 %). However, strain JC130(T) showed less than 32 % DNA reassociation value (based on DNA-DNA hybridization) with Pontibacter korlensis NRRL B-51097(T) ( = X14-1(T)) and Pontibacter actiniarum LMG 23027(T) ( = KMM 6156(T)). Strain JA747(T) was positive for catalase and oxidase activity and negative for nitrate reduction, and hydrolysis of starch and casein. Phosphatidylglycerol, diphostatidylglycerol, phosphatidylethanolamine and phosphatidylcholine were the major polar lipids for strain JA747(T). C18 : 1ω7c, C16 : 1ω6c/C16 : 1ω7c, C17 : 1ω6c and C16 : 0 were the major fatty acids of strain JA747(T). Strain JC130(T) was positive for catalase and oxidase, and negative for gelatinase and nitrate reduction. Phosphatidylethanolamine was the major polar lipid of strain JC130(T). Major fatty acids of strain JC130(T) were iso-C15 : 0 and summed feature 4 (anteiso-C17 : 1B/iso I). Based on the phenotypic, chemotaxonomic and molecular evidence presented, strains JA747(T) and JC130(T) are considered to represent two novel species of the genera Erythrobacter and Pontibacter, for which the names Erythrobacter odishensis sp. nov. (type strain JA747(T) = KCTC 23981(T) = NBRC 108930(T)) and Pontibacter odishensis sp. nov. (type strain JC130(T) = KCTC 23982(T) = LMG 26962(T)), respectively, are proposed. Emended descriptions of the genera Erythrobacter and Pontibacter are provided.

Regulation of simultaneous hydrogen photoproduction during growth by pH and glutamate in Rhodobacter sphaeroides O.U. 001

Onset of simultaneous hydrogen photoproduction in Rhodobacter sphaeroides O.U. 001 occurred during the early stationary phase of growth. The studies on the regulation of onset of hydrogen photoprodaction during growth by pH and glutamate suggest that these parameters affect the total and rates of hydrogen evolution rather than the onset, except at pH 7.5.

Photoproduction of hydrogen from the waste water of a distillery by Rhodobacter sphaeroides O.U. 001

Abstract Waste water from a distillery was used as the electron donor for photoproduction of hydrogen by Rhodobacter sphaeroides O.U. 001. Hydrogen production by free cells was observed only at 5 and 10% waste water (diluted with tap water) yielding a maximum of 500 μl H 2 (in 144 h) at 10% concentration. Calcium alginate immobilization of cells enhanced hydrogen photoproduction two–three fold and hydrogen evolution was observed after varying lag periods at all the concentrations of waste water tested. Semicontinuous culturing of R. sphaeroides was demonstrated in a 3.6 l photobioreactor harvesting 1 l of culture every day amounting to 2 g dry wt. Hydrogen production was demonstrated for 12 days using immobilized cells with 10% waste water in a 3.6 l photobioreactor under light/dark cycles.

Flavobacterium aquaticum sp. nov., isolated from a water sample of a rice field.

Strain JC164(T) was isolated from a water sample from a rice field at Jamdih, Mau, Uttar Pradesh, India. Colonies of strain JC164(T) were brown-yellow and cells were Gram-stain-negative. Catalase, oxidase and amylase were present. iso-C(15:0), iso-C(16:0), iso-C15 1 G, iso-C(15:0) 3-OH and iso-C(14:0) were the predominant fatty acids with minor amounts of iso-C(16:0) 3-OH, anteiso-C(15:0), C(16:0), iso-C(16:1) H, iso-C(14:0) 3-OH and iso-C(13:0). Strain JC164(T) contained phosphatidylethanolamine and a few unidentified lipids (L1, L3 and L6) as major polar lipids. Bacteriohopane derivative 1 (BHD1) and diplopterol (DPL) were the major hopanoids. β-Carotene was one among the several spirilloxanthin series carotenoids present in strain JC164(T). Genomic DNA G+C content was 39.6 mol%. 16S rRNA gene sequence comparisons indicated that strain JC164(T) represents a member of the genus Flavobacterium (family Flavobacteriaceae, class Flavobacteriia). The most closely related taxa to strain JC164(T) were Flavobacterium sasangense YC6274(T) (98.5%), Flavobacterium cucumis R2A45-3(T) (98.1%), Flavobacterium cheniae NJ-26(T) (97.2%) and the novel strain possessed <95.1% sequence similarity with other members of the genus Flavobacterium. However, strain JC164(T) showed 12.5 ± 2, 13.6 ± 1 and 17.4 ± 2% genomic DNA association (based on DNA-DNA hybridization) with Flavobacterium sasangense KCTC 22246(T), Flavobacterium cucumis DSM 18830(T) and Flavobacterium cheniae CGMCC 1.6844(T), respectively. The distinct genomic difference and morphological, physiological and chemotaxonomic differences from the previously described taxa support the classification of strain JC164(T) as a representative of a novel species of the genus Flavobacterium, for which the name Flavobacterium aquaticum sp. nov. is proposed. The type strain is JC164(T) ( = KCTC 32196(T) = CGMCC 1.12398=LMG 27251(T)).

Arcobacter anaerophilus sp. nov., isolated from an estuarine sediment and emended description of the genus Arcobacter.

Two strains (JC83, JC84(T)) of obligately anaerobic, H2S-producing bacteria were isolated from estuarine sediment samples collected from Gangasagar, West Bengal, India. Cells were Gram-stain-negative, non-motile rods. Both strains were positive for oxidase, negative for catalase, hydrolysed casein, reduced nitrate and utilized citrate. Both strains grew chemoorganoheterotrophically with optimal pH of 7-8 (range 7-10) and at 30 °C (range 25-37 °C). C16 : 1ω7c, C18 : 1ω7c, C16 : 0 and C12 : 0 were the major fatty acids of both strains with minor amounts of C14 : 0, C12 : 0 3-OH and C18 : 0. Polar lipids of both strains included diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylserine, phosphatidylcholine, phosphatidylinositol, an unidentified aminolipid (AL2), an unidentified phospholipid (PL2) and an unidentified lipid (L3). MK-6 was the major respiratory quinone. The DNA G+C content of strains JC83 and JC84(T) was 25.0 and 24.6 mol%, respectively. The strains showed DNA reassociation >85 % (86.0±0.5 %) (based on DNA-DNA hybridization). Based on 16S rRNA gene sequence analysis, both strains were identified as belonging to the family Campylobacteraceae of the class Epsilonproteobacteria with Arcobacter marinus CL-S1(T) (95.4 % sequence similarity) as their closest phylogenetic neighbour. On the basis of morphological, physiological and chemotaxonomic characteristics as well as phylogenetic analysis, strains JC83 and JC84(T) are considered to represent a novel species, for which the name Arcobacter anaerophilus sp. nov. is proposed. The type strain is JC84(T) ( = KCTC 15071(T) = MTCC 10956(T) = DSM 24636(T)). An emended description of the genus Arcobacter is provided.

Biotechnological Potentials of Anoxygenic Phototrophic Bacteria. II. Biopolyesters, Biopesticide, Biofuel, and Biofertilizer

Publisher Summary This chapter discusses the biotechnological potentials of anoxygenic phototrophic bacteria II. There is an increasing demand for the use of plasticized (polyester) materials suitable for human needs and many of them which are currently being synthesized chemically are nonbiodegradable and, hence, ecologically not ideal. There is an immediate requirement to replace the nonbiodegradable polyesters by a natural and biodegradable polyester, a waste management option for polymers in the environment, and, in many cases, the demand is driven by legislation. Studies with a number of isolates of anoxygenic phototrophic bacteria suggest that PHA formation is a common phenomenon among this group of microorganisms. In addition, Poly -β -hydroxybutyrate (PHB) is the best-known member of the PHA series of polyesters and it is known to be produced as intracellular energy and carbon reserves which are later utilized by the bacteria for cellular growth.