[Construction and Characterization of B850-Only LH2 Energy Transfer System in Purple Bacteria].

To seek microscopic molecular mechanism of energy transfer and complex reconstitution in the photosynthesis, the conditions for construction of B850-only peripheral light-harvesting complex (LH2) and their properties were investigated using absorption, fluorescence spectroscopy, molecular sieve chromatography, ultrafiltration and sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) from the purple bacteria. The results indicated that bacteriochlorophylls (BChl) of B800 incubated in 10 mmo · L(-1) Tris-HCl (pH 8.0) buffer are selectively released from their binding sites of LH2 of Rhodobacter azotoformans (A-LH2) by 0.08% (W/V) SDS. B850-only A-LH2 was constructed after removing free BChl mixing with 10% methyl alcohol by ultrafiltration. B850 BChl was released after A-LH2 was incubated for 240 min in dark at room temperature (RT). While BChl of B800 incubated in pH 1.9 buffer were selectively released from their binding sites of LH2 of Rhodopseudomonas palustris (P-LH2). The authors acquired two components using molecular sieve chromatography. Free BChl of one component was not removed and self-assembled to P-LH2. The other removed free BChl and B850-only P-LH2 was constructed. B850 unchanged after P-LH2 was incubated. P-LH2 α and ß subunits have different molecular weights, but those of A-LH2 are in the contrary. It is concluded that B850-only P-LH2 is more stable than A-LH2. The enigmatic split of the B800 absorption band was not observed in these LH2, but we acquired two kinds of B800-released LH2 from Rhodopseudomonas palustris. The authors' results may provide a new light to separate homogeneous Apoprotein LH2.

[Influence of LDAO on the conformation and release of bacteriochlorophyll of peripheral light-harvesting complex (LH2) from Rhodobacter azotoformans].

The aim of this study is to reveal the interaction relationships between lauryl dimethylamine N-oxide (LDAO) and peripheral light-harvesting complex (LH2) as well as the influence of LDAO on structure and function of LH2. In the present work, the effects of LDAO on the conformation and release processes of bacteriochlorophyll (BChl) of LH2 when incubated under different temperature and pH in the presence and absence of LDAO were investigated by spectroscopy. The results indicated that (1) the presence of LDAO resulted in alterations in the conformation, alpha-helix content, and spectra of Tyr and B850 band of LH2 at room temperature and pH 8.0. Moreover, energy transfer efficiency of LH2 was enhanced markedly in the presence of LDAO. (2) At 60 degrees C, both the B800 and B850 band of LH2 were released and transited into free BChl at pH 8.0. However, the release rates of bacteriochlorophylls of B800 and B850 band from LH2 were slowed down and the release processes were changed when incubated in the presence of LDAO. Hence, the stability of LH2 was improved in the presence of LDAO. (3) The accelerated release processes of bacteriochlorophylls of B800 and B850 band of LH2 were induced to transform into bacteriopheophytin (BPhe) and free BChl by LDAO in strong acid and strong alkalic solution at room temperature. However, the kinetic patterns of the B800 and B850 band were remarkably different. The release and self-assemble processes of B850 in LH2 were observed in strong acid solution without LDAO. Therefore, the different release behaviors of B800 and B850 of LH2 are induced by LDAO under different extreme environmental conditions.

Mameliella alba gen. nov., sp. nov., a marine bacterium of the Roseobacter clade in the order Rhodobacterales.

A Gram-negative, non-motile, rod-shaped bacterial strain, JLT354-W(T), that accumulates poly-beta-hydroxybutyrate granules was isolated from the South China Sea. Phylogenetic analysis based on 16S rRNA gene sequences showed that the strain was related to members of the genera Antarctobacter, Sagittula, Oceanicola and Loktanella; levels of similarity between strain JLT354-W(T) and members of the above genera were less than 92.0 %. The predominant fatty acid of strain JLT354-W(T) was C(18 : 1)omega7c (83.1 %); significant amounts of C(18 : 0) (7.9 %) and C(12 : 1) 3-OH (3.7 %) were also present. The predominant respiratory ubiquinone was Q-10. The DNA G+C content of strain JLT354-W(T) was 63.7 mol%. The isolate was distinguishable from members of the order Rhodobacterales based on phenotypic and biochemical characteristics. On the basis of the taxonomic data presented, strain JLT354-W(T) is considered to represent a novel species of a new genus, for which the name Mameliella alba gen. nov., sp. nov. is proposed. The type strain of Mameliella alba is JLT354-W(T) (=LMG 24665(T)=CGMCC 1.7290(T)).

Biogeography and phylogeny of the NOR5/OM60 clade of Gammaproteobacteria.

The phylogeny, abundance, and biogeography of the NOR5/OM60 clade was investigated. This clade includes "Congregibacter litoralis" strain KT71, the first cultured representative of marine aerobic anoxygenic phototrophic Gammaproteobacteria. More than 500 16S rRNA sequences affiliated with this clade were retrieved from public databases. By comparative sequence analysis, 13 subclades could be identified, some of which are currently restricted to discrete habitat types. Almost all sequences in the largest subclade NOR5-1 and related subclade NOR5-4 originated from marine surface water samples. Overall, most of the NOR5/OM60 sequences were retrieved from marine coastal settings, whereas there were fewer from open-ocean surface waters, deep-sea sediment, freshwater, saline lakes and soil. The abundance of members of the NOR5/OM60 clade in various marine sites was determined by fluorescence in situ hybridization using a newly designed and optimized probe set. Relative abundances in coastal marine waters off Namibia and the Yangtze estuary were up to 3% of the total 4',6-diamidino-2-phenylindole (DAPI) counts, and in the German Bight off Helgoland the abundance was even up to 7%. In an open-ocean North Atlantic transect, between Iceland and the Azores, the NOR5/OM60 group was much less abundant (0.1-0.5%). Interestingly, the surface layer of North Sea intertidal sediments was very rich in NOR5/OM60, with absolute numbers >10(8) cells cm(-3) (or 4% of the total DAPI). An analysis of the frequencies of NOR5/OM60 16S rRNA genes in the Global Ocean Survey datasets provided further support for a marine cosmopolitan occurrence of NOR5/OM60, and a clear preference for coastal marine waters.

Yangia pacifica gen. nov., sp. nov., a novel member of the Roseobacter clade from coastal sediment of the East China Sea.

An aerobic, Gram-negative bacterial isolate, strain DX5-10T, was isolated from coastal sediment of the East China Sea. The taxonomy of strain DX5-10T was studied by phenotypic and phylogenetic methods. Strain DX5-10T was motile, formed faint-yellowish colonies and was positive for catalase reaction and weakly positive for oxidase reaction. The nearly complete 16S rRNA gene of strain DX5-10T was obtained and sequence analysis indicated that strain DX5-10T represented an independent lineage within the Roseobacter clade of Alphaproteobacteria. Strain DX5-10T was phylogenetically related to members of the genera Roseobacter, Loktanella, Roseisalinus, Silicibacter, Antarctobacter, Sulfitobacter, Salipiger, Ruegeria and Roseivivax, and the sequence identities among them were less than 95.0%. The predominant respiratory ubiquinone of strain DX5-10T was Q-10 and the DNA G + C content of strain DX5-10T was 63.3 mol%. Therefore, strain DX5-10T represents a novel species of a novel genus, for which the name Yangia pacifica gen. nov., sp. nov. is proposed, with the type strain DX5-10T (= CGMCC 1.3455T = JCM 12573T).

[Bacterial conversion of sulfur-and phosphorous-compounds and microbial diversity in sediments from a near-shore marine-cultural region].

The H2S-producing bacteria and the phosphorous-cycling bacteria in sediments from near-shore marine-cultural region were investigated. Results indicate that the bacterial H2S production in aerobic condition is the dominating process to produce H2S in the sediment of cultural pond. The total counts of H2S-producing bacteria utilizing cysteine and Na2S2O3 were 1.6 x 10(6) and 4.35 x 10(3) cells g(-1) respectively. The counts of sulfate-reducing bacteria in the sediments were very little, only 2.5 x 10(1) g(-1). Further results show that the bacterial counts of decomposing lecithin and secreting phosphatase were 2.17 x 10(5) and 1.21 x 10(6) g(-1) respectively, bacterial counts of dissolving Ca3PO4 were 6.96 x 10(3) g(-1). Traditional taxonomy and partial 16S rRNA gene sequencing on the H2S-producing and phosphate-cycling bacteria indicate that most isolates could be classified as members of the following Genera: Bacillus, Halobacillus, Microbacterium, etc.

Evolution of nutrient structure and phytoplankton composition in the Jiaozhou Bay ecosystem.

The inventories of nutrients in the surface water and large phytoplankton( > 69 microm) were analyzed from the data set of JERS ecological database about a typical coastal waters, the Jiaozhou Bay, China, from 1960s for N, P and from 1980s for Si. By examining long-term changes of nutrient concentration, calculating stoichiometric balance, and comparing diatom composition, Si limitation of diatom production was found to be more possible. The possibility of Si limitation was from 37% in 1980s to 50% in 1990s. Jiaozhou Bay ecosystem is becoming serious eutrophication, with notable increase of NO2-N, NO3-N and NH4-N from 0.1417 micromol/L, 0.5414 micromol/L, 1.7222 micromol/L in 1960s to 0.9551 micromol/L, 3.001 micromol/L, 8.0359 micromol/L in late 1990s respectively and prominent decrease of Si from 4.2614 micromol/L in 1980s to 1.5861 micromol/L in late 1990s; the nutrient structure is controlled by nitrogen; the main limiting nutrient is probably silicon; because of the Si limitation the phytoplankton community structure has changed drastically.