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Aerobic anoxygenic phototrophic bacteria (AAnPB) are bacteriochlorophyll a-containing photoheterotrophic organisms that rely on phototrophy and heterotrophy processes for energy acquisition. Here, we demonstrate the ubiquitous distribution of AAnPB in the Uwa Sea and their relatively larger cell size among members of the bacteria community. The contribution of AAnPB in terms of cell number to the total bacterial abundance ranged from 3.5 % to 7.9 %. The mean cell volume for AAnPB was 2.78 ± 0.72 times larger than the mean cell volume of the total bacteria. The ratio of the contribution of their biovolume to the total bacteria was estimated to be 9.7-22 %. [ABSTRACT FROM AUTHOR]

The article offers information on a study related to removal of radioactivity from soil in Fukushima-ken, Japan. It informs about the removal of radioactivity from polluted soil in Fukushima-ken was done using a photosynthetic bacterium, rhodobacter spliaeroides SSI, immobilized in alginate beads by aerobic treatments.

The article cites a research study that describes the removal of radioactivity from sediment mud in a swimming pool by immobilized photosynthetic bacteria. The alginate immobilized photosynthetic bacterium Rhodobcater sphaeroides SSI was used to remove about 90% of the radioactive Cs in the sediment mud of a school's swimming pool in Fukushima, Japan.

Abstract: Photosynthetic bacteria produce hydrogen from lactate and acetate that are products of hydrogen producing bacteria in the dark. Thus, their coculture is a promising method for hydrogen production. However, the hydrogen production yield from acetate of Rhodobacter sphaeroides RV, which has been shown to possess the highest yield and hydrogen production rate, is low as compared to that from lactate. Photosynthetic bacteria that produce hydrogen from acetate as well as lactate were screened from lakes and swamps in the Tokyo and Chiba areas in Japan. Seventy-six strains of photosynthetic bacteria were obtained and the analysis of their 16S rRNA gene sequences revealed that they belong to R. sphaeroides. Among the isolated bacteria, R. sphaeroides HJ produced the highest amount of hydrogen from acetate and lactate. The HJ strain produced a 2300±93ml/L-broth of hydrogen from 75mM acetate consumed during for 120h of fermentation. The amount of hydrogen and the yield from acetate were 1.9 and 2.1 times higher, respectively, than those of R. sphaeroides RV. The amount and yield of hydrogen, produced by R. sphaeroides HJ from lactate were similar to those produced by R. sphaeroides RV. Since the amount and yield of produced hydrogen by the HJ strain were similar regardless of the substrate (acetate or lactate), its metabolic pathway could have a key to increasing hydrogen production from acetate. [Copyright &y& Elsevier]

Abstract: At the Nakabusa hot spring, Japan, dense olive-green microbial mats develop in regions where the slightly alkaline, sulfidic effluent has cooled to 65°C. The microbial community of such mats was analyzed by focusing on the diversity, as well as the in situ distribution and function of bacteria involved in sulfur cycling. Analyses of 16S rRNA and functional genes (aprA, pufM) suggested the importance of three thermophilic bacterial groups: aerobic chemolithotrophic sulfide-oxidizing species of the genus Sulfurihydrogenibium (Aquificae), anaerobic sulfate-reducing species of the genera Thermodesulfobacterium/Thermodesulfatator, and filamentous anoxygenic photosynthetic species of the genus Chloroflexus. A new oligonucleotide probe specific for Sulfurihydrogenibium was designed and optimized for catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH). In situ hybridizations of thin mat sections showed a heterogeneous vertical distribution of Sulfurihydrogenibium and Chloroflexus. Sulfurihydrogenibium dominated near the mat surface (50% of the total mat biovolume), while Chloroflexus dominated in deeper layers (up to 64% of the total mat biovolume). Physiological experiments monitoring in vitro changes of sulfide concentration indicated slight sulfide production by sulfate-reducing bacteria under anoxic-dark conditions, sulfide consumption by photosynthetic bacteria under anoxic-light conditions and strong sulfide oxidation by chemolithotrophic members of Aquificae under oxic-dark condition. We therefore propose that Sulfurihydrogenibium spp. act as highly efficient scavengers of oxygen from the spring water, thus creating a favorable, anoxic environment for Chloroflexus and Thermodesulfobacterium/Thermodesulfatator in deeper layers. [Copyright &y& Elsevier]

Abstract: Photosynthetic influences on tufa stromatolite formation and ambient water chemistry were investigated at two well-studied streams depositing tufa in Southwestern Japan (Shirokawa and Shimokuraida). The tufa stromatolites in both streams are composed of fine-grained calcite crystals showing annual lamination, and colonized by a number of filamentous cyanobacteria as well as non-phototrophic bacteria. Microelectrode measurements of pH, O2, and Ca2+ near the stromatolite surface (the diffusive boundary layer; DBL) revealed that the investigated tufa stromatolites are formed by photosynthesis-induced CaCO3 precipitation (PCP): cyanobacterial photosynthesis induces calcite precipitation under light conditions, while respiration of cyanobacteria and non-phototrophic bacteria inhibits precipitation in the dark. The bulk water chemistry at the lower sites of the investigated streams showed the daytime decreases of Ca2+ concentration and alkalinity that was expected for significant influence of PCP, while the other expected change, increased pH, was not observed. In order to examine this discrepancy, a novel approach using semi-in situ microelectrode measurements was applied to perform precise quantitative calculations. The calculation results demonstrated that the observed Ca2+ concentration and alkalinity decreases were caused by PCP, and that the concomitant pH increase was expected to be under the detection level of a conventional pH meter. Although the amount of PCP is supposed to be significantly affected by light intensity, observations in Shimokuraida revealed that the amount of PCP on cloudy day nonetheless accounted for about 80% of that on sunny day. Despite the significant role of PCP for tufa stromatolite formation, PCP accounted for only about 10% of the precipitated calcite in the investigated streams, which indicates that tufa stromatolites, the characteristic deposits in the streams, are responsible for only a small portion of calcite precipitation, and the rest is considered to precipitate inorganically at biofilm-free substrates. [Copyright &y& Elsevier]

Abstract  The photosynthetic and respiratory responses of Gracilaria salicornia in the subtropical waters of Japan (in Okinawa) and in the tropical waters of Thailand (in Rayong and Phuket Provinces), were studied under various conditions of irradiance, salinity and temperature. This alga showed adaptability in its photosynthetic and respiratory responses to oceanic salinity as well as to subtropical to tropical temperature. Significant differences in the photosynthetic and respiratory rates among the G. salicornia populations collected from the above sites were observed. The Phuket population showed adaptability to high irradiance and temperature, characteristic of its natural sun-exposed environment, as it exhibited the highest I k and I c, and lowest α and higher P max at 30–35�C. On the other hand, the Okinawa population demonstrated adaptability to low submarine irradiance as it had a lower I k and I c than either population from Thailand. Its P max at 20–25�C was also higher than that of the Phuket population. The Rayong population, however, showed the highest P max, Rd, α, I k and I c, suggesting its adaptability to both sun and shade light conditions in its natural environment. [ABSTRACT FROM AUTHOR]

Aerobic anoxygenic phototrophic bacteria (AAnPB) are widely distributed and regarded as key players driving the carbon cycle in surface water of global oceans, coastal and estuary areas and in other freshwater environments (e.g., ponds and lakes). However, the abundance and spatial distribution of AAnPB in rivers is much less well-known. Here we investigated the variation of the absolute cell abundances of the total bacteria, AAnPB and cyanobacteria, at four different sites in Tama River, Japan, and the spatial distribution (i.e., free-living or particle-attached existence form) of AAnPB at two out of the four sites using infra-red epifluorescence microscopy. Free-living cell abundances for the total bacteria, AAnPB and cyanobacteria were 1.6–3 × 105, 1.5–4.4 × 104 and <3.2 × 104 cells mL−1, respectively. The free-living AAnPB accounted for 6.1%–19.6% of the total bacterial abundance in the river. The peaks of the AAnPB and cyanobacteria abundances were found at the same site, suggesting that the AAnPB could potentially coexist with cyanobacteria. Meanwhile, the particle-attached AAnPB were observed at the two sites of the river, accounting for 52.2% of the total bacteria abundance in the particle. Our results showed the existence and aggregation form of AAnPB in the riverine environment. [ABSTRACT FROM AUTHOR]

Presents abstracts of studies on new advances in plant research motivated by determination of Cyanidioschyzon merolae genome, presented at the 68th Annual Meeting of the Botanical Society of Japan held at the Shonan Campus of Nihon University in Japan from September 9 to 12, 2004. "A Whole Picture of the Cyanidioschyzon Merolae Genome," by Motomichi Matsuzaki; "Comparative Genomics of Photosynthetic Organisms," by Naoki Sato; "Future Prospects of Studies on C. Merolae as a Model Plant: Culture, Distributions, Resources, Etc.," by Osami Misumi.

Phototrophic microbial mats are assemblages of vertically layered microbial populations dominated by photosynthetic microorganisms. In order to elucidate the vertical distribution and diversity of phototrophic microorganisms in a hot spring-associated microbial mat in Nakabusa (Japan), we analyzed the 16S rRNA gene amplicon sequences of the microbial mat separated into five depth horizons, and correlated them with microsensor measurements of O 2 and spectral scalar irradiance. A stable core community and high diversity of phototrophic organisms dominated by the filamentous anoxygenic phototrophs, Roseiflexus castenholzii and Chloroflexus aggregans were identified together with the spectral signatures of bacteriochlorophylls (BChls) a and c absorption in all mat layers. In the upper mat layers, a high abundance of cyanobacteria (Thermosynechococcus sp.) correlated with strong spectral signatures of chlorophyll a and phycobiliprotein absorption near the surface in a zone of high O 2 concentrations during the day. Deeper mat layers were dominated by uncultured chemotrophic Chlorobi such as the novel putatively sulfate-reducing "Ca. Thermonerobacter sp.", which showed increasing abundance with depth correlating with low O 2 in these layers enabling anaerobic metabolism. Oxygen tolerance and requirements for the novel phototroph "Ca. Chloroanaerofilum sp." and the uncultured chemotrophic Armatimonadetes member type OS-L detected in Nakabusa hot springs, Japan appeared to differ from previously suggested lifestyles for close relatives identified in hot springs in Yellowstone National Park, USA. The present study identified various microenvironmental gradients and niche differentiation enabling the co-existence of diverse chlorophototrophs in metabolically diverse communities in hot springs.

The genus Chloroflexus is a deeply branching group of thermophilic filamentous anoxygenic phototrophic bacteria. The bacteria in this genus have been shown to grow well heterotrophically under anaerobic photosynthetic and aerobic respiratory conditions. We examined autotrophic growth in new isolates of Chloroflexus strains from hot springs in Nakabusa, Japan. The isolates belonging to Chloroflexus aggregans (98.7% identity of 16S rRNA gene sequence to the respective type strain) and Chloroflexus aurantiacus (99.9% identity to the respective type strain) grew photoautotrophically under a 24% H2 atmosphere. We also observed chemolithotrophic growth of these isolates under 80% H2 and 5% O2 conditions in the dark. This is the first report showing that Chloroflexus grew under both photoautotrophic and chemolithotrophic conditions in addition to photoheterotrophic and aerobic chemoheterotrophic conditions. [ABSTRACT FROM AUTHOR]