Photosynthetic bacteria emerged on Earth more than 3 Gyr ago. To date, despite a long evolutionary history, species containing (bacterio)chlorophyll-based reaction centers have been reported in only 6 out of more than 30 formally described bacterial phyla: Cyanobacteria, Proteobacteria, Chlorobi, Chloroflexi, Firmicutes, and Acidobacteria. Here we describe a bacteriochlorophyll a-producing isolate AP64 that belongs to the poorly characterized phylum Gemmatimonadetes. This red-pigmented semiaerobic strain was isolated from a freshwater lake in the western Gobi Desert. It contains fully functional type 2 (pheophytin-quinone) photosynthetic reaction centers but does not assimilate inorganic carbon, suggesting that it performs a photoheterotrophic lifestyle. Full genome sequencing revealed the presence of a 42.3-kb-long photosynthesis gene cluster (PGC) in its genome. The organization and phylogeny of its photosynthesis genes suggests an ancient acquisition of PGC via horizontal transfer from purple phototrophic bacteria. The data presented here document that Gemmatimonadetes is the seventh bacterial phylum containing (bacterio)chlorophyllbased phototrophic species. To our knowledge, these data provide the first evidence that (bacterio)chlorophyll-based phototrophy can be transferred between distant bacterial phyla, providing new insights into the evolution of bacterial photosynthesis.anoxygenic photosynthesis | horizontal gene transfer | bacterial pigments | aerobic photoheterotroph | fluorescence imaging system

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We studied the distribution of anoxygenic phototrophs in 23 steppe lakes in the Transbaikal region (Russia), in Uzbekistan (Central Asia) and in the Crimean peninsula (Ukraine). The lakes varied in their mineral content and composition (salinities from 0.2 to 300 g L À1 ). The Transbaikal lakes were alkaline (pH 4 9), with high amounts of soda. The Uzbek and Crimean lakes were more pH neutral, frequently with high amounts of sulfates. The presence of anoxygenic phototrophs was registered by infrared epifluorescence microscopy, infrared fluorometry and pigment analyses. In mostly shallow, fully oxic lakes, the anoxygenic phototrophs represented 7-65% of the total prokaryotes, with the maxima observed in Transbaikal soda lakes Gorbunka (32%), Khilganta (65%), Zanday (58%) and Zun-Kholvo (46%). Some of the lakes contained over 1 mg bacteriochlorophyll L À1 .In contrast, only small amounts of anoxygenic phototrophs were present in highly mineralized lakes ( 4 100 g total salts L À1 ); Borzinskoe, Tsagan-Nur (Transbaikal), Staroe (Crimea) and in the residual part of the south-west Aral Sea (Uzbekistan). The oxic environment and the specific diurnal changes of bacteriochlorophyll concentration observed suggest that the phototrophic community was mostly composed of aerobic anoxygenic phototrophs. The high abundances and bacteriochlorophyll concentrations point to an important role of aerobic anoxygenic phototrophs in the habitats studied.

Peat bog lakes represent important ecosystems in temperate and boreal zones. We investigated the seasonal dynamics of the microbial community in two small peat bog lakes, Kuźnik Olsowy and Kuźnik Bagienny, located in western Poland. Fluorescence in situ hybridization analyses revealed that the bacterial community was dominated by Proteobacteria and Actinobacteria, in addition to a substantial number of archaea. An infrared epifluorescence analysis demonstrated that aerobic anoxygenic phototrophs (AAPs) constituted a significant fraction of bacterial plankton (1-19%). All the bacterial groups exhibited large seasonal changes whose course differed between the studied lakes. While chlorophyll had its maximum during winter or early summer, AAPs peaked in summer, when the growth of this group was stimulated by higher irradiance and elevated water temperatures.

The title ligand, 1,4,8,11-tetraazacyclotetradecane-1,4-diyl-bis(methylphosphonic acid) (H4te2p1,4, H4L), was prepared by an optimized synthetic approach and its complexing properties towards selected metal ions were studied by means of potentiometry. The ligand forms a very stable complex with copper(II) (log beta(CuL) = 27.21), with a high selectivity over binding of other metal ions (e.g. log beta(ZnL) = 20.16, log beta(NiL) = 21.92). The crystal structures of two intermediates in the ligand synthesis and two forms of the nickel(II) complex (obtained by crystallization at different pH) were determined. From acid solution, the crystals of trans-O,O-[Ni(H3L)]Cl.H2O were isolated. In such complex species, one phosphonate pendant arm is double- and the second arm is monoprotonated. The isolation of such species demonstrates a high kinetic inertness of the complex. The central metal ion is surrounded by four in-plane nitrogen atoms (in the ring configuration III) and two oxygen atoms of pendant moieties in the apical positions of octahedral coordination sphere. From neutral solution, the crystals of (trans-O,O-[Ni(H2L)])3.5H2O were isolated. The molecular structures of the complex units found in this structure are analogous to that found in trans-O,O-[Ni(H3L)]Cl.H2O.

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The planktonic and benthic microbial communities in 8 hypersaline evaporation ponds of the Israel Salt Company in Eilat, Israel, with salinities ranging from 58 to 329 g l -1 (total dissolved salt), were studied using fluorescence emission spectroscopy and kinetic fluorometry. With increasing salinity, the anoxygenic phototrophic bacteria (containing bacteriochlorophyll a, bchl a) formed a significant and increasing fraction of the planktonic phototrophic biomass. While the bchl a/chl a molar ratio was 0.01 at the lowest salinity, it reached almost 1 at the higher salinities. In the benthic communities, emission spectroscopy revealed depth-dependent changes in the photophysiology of benthic oxygenic phototrophs, and spatial variability in the abundance of several groups of anoxygenic photosynthetic bacteria (green bacteria containing chlorosomes and purple bacteria containing LH1). In general, the emission signal of the benthic oxygenic phototrophs (diatoms and Cyanobacteria) was dominated by photosystem I (detected in some cases down to 5 cm of sediment depth). The signal of photosystem II and phycobilisomes was several times weaker and was observed mostly in the surface layers. The spectroscopic data of microbial communities were complemented by microscopic characterization.

Temperature is one of the most important physical factors affecting microbial and biochemical processes. We investigated the performance of photosynthetic apparatus of marine photoheterotrophic bacterium Dinoroseobacter shibae under various temperatures. The primary photochemistry and electron transport was measured using variable infra-red fluorometry in the cells grown between 8-35°C. It was found that the photosynthetic electron transport had a broad temperature optimum between 25-50°C. Moreover, the primary charge separation stayed functional even after rising temperature up to 55°C. The same phenomenon was observed also in other phototrophic Rhodobacterales. The psychrotolerant bacterium Roseisalinus antarcticus reached its maximum electron transport rate at 48°C, 30°C above its growth temperature. We propose that the extended temperature stability may be crucial to maintain photosynthetic function under situation when photosynthetic membranes heat up above their ambient temperature due to the heat dissipation of the excess light energy.