Aerobic Anoxygenic Photosynthetic Bacteria Research Articles

Genomic Analysis and Characterization of Pseudotabrizicola formosa sp. nov., a Novel Aerobic Anoxygenic Phototrophic Bacterium, Isolated from Sayram Lake Water.

Aerobic anoxygenic photosynthetic bacteria (AAPB) are a kind of heterotrophic prokaryote that can use bacteriochlorophyll (BChl) for photosynthesis without oxygen production and they are widely distributed in aquatic environments, including oceans, lakes, and rivers. A novel aerobic anoxygenic photosynthetic bacterium strain XJSPT was isolated during a study of water microbial diversity in Sayram Lake, Xinjiang Province, China. Strain XJSPT was found to grow optimally at 33 °C, pH 7.5 with 1.0% (w/v) NaCl, and to produce bacteriochlorophyll a and carotenoids. Phylogenetic analysis based on 16S rRNA gene sequence and concatenated alignment sequences of 120 ubiquitous single-copy proteins both supported that strain XJSPT belonged to the genus Pseudotabrizicola. Both average nucleotide identity (ANI) and DNA-DNA hybridization (DDH) values were below the species delineation threshold. The primary polar lipids were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, one unknown lipid, and one unidentified phospholipid. Based on the results of polyphasic analyses performed in this study, strain XJSPT represents a new member of the genus Pseudotabrizicola, for which the name Pseudotabrizicola formosa sp. nov. is proposed. The type strain is XJSPT (=KCTC 52636T = MCCC 1H00184T = SDUM 107003T). Comparative genomic analysis showed that four species of the genus Pseudotabrizicola shared 2570 core genes and possessed a complete anoxygenic photosystem II.

Type II Photosynthetic Reaction Center Genes of Avocado (Persea americana Mill.) Bark Microbial Communities are Dominated by Aerobic Anoxygenic Alphaproteobacteria.

The tree bark environment is an important microbial habitat distributed worldwide on thrillions of trees. However, the microbial communities of tree bark are largely unknown, with most studies on plant aerial surfaces focused on the leaves. Recently, we presented a metagenomic study of bark microbial communities from avocado. In these communities, oxygenic and anoxygenic photosynthesis genes were very abundant, especially when compared to rhizospheric soil from the same trees. In this work, Evolutionary Placement Algorithm analysis was performed on metagenomic reads orthologous to the PufLM gene cluster, encoding for the bacterial type II photosynthetic reaction center. These photosynthetic genes were found affiliated to different groups of bacteria, mostly aerobic anoxygenic photosynthetic Alphaproteobacteria, including Sphingomonas, Methylobacterium and several Rhodospirillales. These results suggest that anoxygenic photosynthesis in avocado bark microbial communities functions primarily as additional energy source for heterotrophic growth. Together with our previous results, showing a large abundance of cyanobacteria in these communities, a picture emerges of the tree holobiont, where light penetrating the tree canopies and reaching the inner stems, including the trunk, is probably utilized by cyanobacteria for oxygenic photosynthesis, and the far-red light aids the growth of aerobic anoxygenic photosynthetic bacteria.

Mixed-culture aerobic anoxygenic photosynthetic bacterial consortia reduce nitrate: Core species dynamics, co-interactions and assessment in raw water of reservoirs

Three consortia of mixed-culture Aerobic Anoxygenic Photosynthetic Bacteria (AAPB) with excellent aerobic denitrifying ability were isolated from drinking water source reservoirs. The results showed that the removal of dissolved organic carbon (DOC) and nitrate nitrogen (NO3–-N) by mixed-culture AAPB were higher than 90% and 99%, respectively. The Illumina MiSeq sequencing of pufM gene revealed that the dominant genera and their relative abundance changed over the culture periods. Sphingomonas sanxanigenens was the most dominant species observed at 9 h, whereas at 48 h, the most abundant species was Rhodobacter blasticus. A network analysis demonstrated that the co-interactions among the different genera were complex and variable. Mixed-culture AAPB removed more than 30% of NO3–-N and 25% of DOC from the source water and this study suggests that mixed-culture AAPB can be regarded as a latent denitrifying microbial inoculum in the reservoir raw water treatment.

Whole-Genome Sequence of a Unique Elioraea Species Strain Isolated from a Yellowstone National Park Hot Spring.

The genus Elioraea has only one species characterized microbiologically and two genomes sequenced. We have sequenced the genome of a unique Elioraea strain isolated from Yellowstone National Park and found it to be a distinct new species. Elioraea is suggested to be a member of the aerobic anoxygenic photosynthetic bacteria.

Nonlinear effect of irradiance on photoheterotrophic activity and growth of the aerobic anoxygenic phototrophic bacterium Dinoroseobacter shibae.

Aerobic anoxygenic photosynthetic bacteria are an important component of marine microbial communities. They produce energy in light using bacteriochlorophyll a containing photosystems. This extra energy provides an advantage over purely heterotrophic bacteria. One of the most intensively studied AAP bacteria is Dinoroseobacter shibae, a member of the environmentally important Roseobacter clade. Light stimulates its growth and metabolism, but the effect of light intensity remains unclear. Here, we show that an increase in biomass along an irradiance gradient followed the exponential rise to the maximum curve, with saturation at about 300 µmol photons m-2 s-1 , without any inhibition at light intensities up to 600 µmol photons m-2 s-1 . The cells adapted to higher irradiance by reducing pigmentation and increasing the electron transfer rate. This additional energy allowed D. shibae to redirect the metabolism of organic carbon sources such as glucose, leucine, glutamate, acetate and pyruvate toward anabolism, resulting in a twofold increase of their assimilation rates. We provide equations that can be feasibly incorporated into the existing model of D. shibae metabolism to further advance our understanding of the role of photoheterotrophy in the ocean.

Requirement of dark culture condition for enlargement of spheroplasts of the aerobic anoxygenic photosynthetic marine bacterium Erythrobacter litoralis.

In the present study, spheroplasts from the aerobic anoxygenic photosynthetic marine bacterium Erythrobacter litoralis were generated and cultivated. In the presence of penicillin, the spheroplasts grew and enlarged in marine broth without undergoing cell division. However, continuous light inhibited their enlargement, and they were therefore cultivated in the dark. Cellular DNA was quantified at various time points (0, 24, and 48 h) and temperatures (20°C, 25°C, and 30°C) using real-time quantitative PCR. The DNA content was highest at 30°C in the absence of penicillin, whereas there was no observable change with exposure to penicillin at all evaluated temperatures. During growth, larger spheroplasts were more frequently observed at 25°C in the presence of penicillin. These results demonstrate that the optimal culture conditions for the enlargement of spheroplasts in E. litoralis differ from those required for cell division.

Characterization of giant spheroplasts generated from the aerobic anoxygenic photosynthetic marine bacterium Roseobacter litoralis.

We generated and characterized giant spheroplasts from the aerobic anoxygenic photosynthetic marine bacterium Roseobacter litoralis. The giant spheroplasts contained vacuole-like structures within the cells, mainly consisting of a single membrane. The in vivo absorption spectrum of the giant spheroplasts did not have peaks typically observed for bacteriochlorophyll a. The culture media pH decreased during the growth of the giant spheroplasts. The change in the pH profile for cells grown under light was no different from that for cells grown in the dark. These results showed that the R. litoralis giant spheroplasts formed lost their photosynthetic apparatus in culture. Most of the giant spheroplasts returned to their original size, likely via filamentous cells. The culture media pH increased during the growth of the filamentous cells. Some filamentous cells had septum-like structures. In such filamentous cells, DNA was separated. Initially, the color of the separated cells was white. Two weeks later, the cells changed to red in the dark, and the in vivo absorption spectrum of the cells had peaks typically observed for bacteriochlorophyll a. Our findings strongly suggest that the giant spheroplasts of R. litoralis can control the genetic information, return to their original cell size, and regain their original functions.

Characterization of giant spheroplasts generated from the aerobic anoxygenic photosynthetic marine bacterium Roseobacter litoralis.

DNA extracted from the bacterial culture used in this paper was analyzed by the massively parallel DNA sequencing. The sequence similarity search showed that most of the obtained DNA sequences were similar to those of Enterobacter genomic DNA. PCR analyses using primers to detect Enterobacter DNA showed that the original Roseobacter culture was contaminated with this bacterium. The authors recognized that the cultures used in this paper were considered as a mixture of Enterobacter and Roseobacter litoralis, and the deduced results were not well rationalized. Thus, the JGAM editorial board agreed to retract the paper.

High Ratio of Bacteriochlorophyll Biosynthesis Genes to Chlorophyll Biosynthesis Genes in Bacteria of Humic Lakes

Recent studies highlight the diversity and significance of marine phototrophic microorganisms such as picocyanobacteria, phototrophic picoeukaryotes, and bacteriochlorophyll- and rhodopsin-holding phototrophic bacteria. To assess if freshwater ecosystems also harbor similar phototroph diversity, genes involved in the biosynthesis of bacteriochlorophyll and chlorophyll were targeted to explore oxygenic and aerobic anoxygenic phototroph composition in a wide range of lakes. Partial dark-operative protochlorophyllide oxidoreductase (DPOR) and chlorophyllide oxidoreductase (COR) genes in bacteria of seven lakes with contrasting trophic statuses were PCR amplified, cloned, and sequenced. Out of 61 sequences encoding the L subunit of DPOR (L-DPOR), 22 clustered with aerobic anoxygenic photosynthetic bacteria, whereas 39 L-DPOR sequences related to oxygenic phototrophs, like cyanobacteria, were observed. Phylogenetic analysis revealed clear separation of these freshwater L-DPOR genes as well as 11 COR gene sequences from their marine counterparts. Terminal restriction fragment length analysis of L-DPOR genes was used to characterize oxygenic aerobic and anoxygenic photosynthesizing populations in 20 lakes differing in physical and chemical characteristics. Significant differences in L-DPOR community composition were observed between dystrophic lakes and all other systems, where a higher proportion of genes affiliated with aerobic anoxygenic photosynthetic bacteria was observed than in other systems. Our results reveal a significant diversity of phototrophic microorganisms in lakes and suggest niche partitioning of oxygenic and aerobic anoxygenic phototrophs in these systems in response to trophic status and coupled differences in light regime.

Genetic diversity of aerobic anoxygenic photosynthetic bacteria in open ocean surface waters and upper twilight zones

Aerobic anoxygenic phototrophic bacteria (AAPB) represent a widespread mixotrophic bacterial group in marine ecosystems. Here we investigated AAPB genetic diversity in the surface waters and upper twilight zones of the central Pacific, Atlantic, and Indian oceans by amplifying an AAPB marker gene (pufM, encoding photosynthetic reaction center small subunit) directly from bacterioplankton community DNA. Phylogenetic and statistical analysis of 267 pufM partial sequences in six clone libraries revealed a high diversity pattern in open ocean AAPB communities. Various AAPB subgroups belonging to Alpha- and Gamma-proteobacteria were found in both surface and upper twilight zone waters. In most samples, subgroups in which no pure culture was isolated as yet were predominant. By sampling a wide size range of bacterioplankton (0.22–200 μm) and introducing nested PCR to amplification, we retrieved abundant pufM fragments (136 sequences in 37 OTUs) directly from upper twilight zone samples. AAPB populations in upper twilight zones covered major subgroups found in surface waters and had a slightly lower diversity, higher dominance, and lower GC and GC3 contents in pufM genes than those in surface AAPB populations. These diversity data combined with previous BChl.a data in upper twilight zones support the hypothesis that AAPB may be present below euphotic zones based on the speculation that AAPB can utilize the dim light in twilight zones as a supplement to energy supply in their heterotrophic lives.

The use of denaturing gradient gel electrophoresis with fully degenerate pufM primers to monitor aerobic anoxygenic phototrophic assemblages

Aerobic Anoxygenic Photosynthetic bacteria (AAnP) were recently proposed to be significant contributors to the global ocean carbon and energy cycles, but relatively little is known about the spatial and temporal distribution of AAnP populations. Here, we report on the development of denaturing gradient gel electrophoresis (DGGE) analyses to monitor naturally occurring marine AAnP populations using the pufM gene. We developed an approach using fully degenerate universal pufM primers, and tested the effect of different primers and PCR conditions on DGGE band resolution and migration. PufM‐DGGE analyses of eastern Mediterranean environmental DNA samples show that AAnP composition was coherent among stations and seasons. Furthermore, samples from different depths of stratified water columns resulted in clearly different DGGE patterns, while very similar DGGE patterns at varying depths were observed under well‐mixed conditions. These results demonstrate the potential use of DGGE with fully degenerate primers as a tool for rapid analyses of natural marine AAnP communities.

Control of Peripheral Light-Harvesting Complex Synthesis by a Bacteriophytochrome in the Aerobic Photosynthetic Bacterium Bradyrhizobium Strain BTAi1

The recent sequence analysis of the photosynthetic and plant-symbiotic Bradyrhizobium sp. strain BTAi1 revealed the unexpected presence of a pucBA operon encoding the apoproteins of peripheral light-harvesting (LH) complexes. This pucBA operon is found close to a bacteriophytochrome gene (BphP3(B BTAi1)) and a two-component transcriptional regulator gene (TF(BTAi1) gene). In this study, we show that BphP3(B BTAi1) acts as a bona fide bacteriophytochrome and controls, according to light conditions, the expression of the pucBA operon found in its vicinity. This light regulatory pathway is very similar to the one previously described for chromo-BphP4(Rp) in Rhodopseudomonas palustris and conducts the synthesis of a peripheral LH complex. This LH complex presents a single absorption band at low temperature, centered at 803 nm. Fluorescence emission analysis of intact cells indicates that this peripheral LH complex does not act as an efficient light antenna. One putative function of this LH complex could be to evacuate excess light energy in order to protect Bradyrhizobium strain BTAi1, an aerobic anoxygenic photosynthetic bacterium, against photooxidative damage during photosynthesis.

High Abundances of Aerobic Anoxygenic Photosynthetic Bacteria in the South Pacific Ocean

Little is known about the abundance, distribution, and ecology of aerobic anoxygenic phototrophic (AAP) bacteria, particularly in oligotrophic environments, which represent 60% of the ocean. We investigated the abundance of AAP bacteria across the South Pacific Ocean, including the center of the gyre, the most oligotrophic water body of the world ocean. AAP bacteria, Prochlorococcus, and total prokaryotic abundances, as well as bacteriochlorophyll a (BChl a) and divinyl-chlorophyll a concentrations, were measured at several depths in the photic zone along a gradient of oligotrophic conditions. The abundances of AAP bacteria and Prochlorococcus were high, together accounting for up to 58% of the total prokaryotic community. The abundance of AAP bacteria alone was up to 1.94 x 10(5) cells ml(-1) and as high as 24% of the overall community. These measurements were consistent with the high BChl a concentrations (up to 3.32 x 10(-3) microg liter(-1)) found at all stations. However, the BChl a content per AAP bacterial cell was low, suggesting that AAP bacteria are mostly heterotrophic organisms. Interestingly, the biovolume and therefore biomass of AAP bacteria was on average twofold higher than that of other prokaryotic cells. This study demonstrates that AAP bacteria can be abundant in various oligotrophic conditions, including the most oligotrophic regime of the world ocean, and can account for a large part of the bacterioplanktonic carbon stock.

Assessing diversity and biogeography of aerobic anoxygenic phototrophic bacteria in surface waters of the Atlantic and Pacific Oceans using the Global Ocean Sampling expedition metagenomes

Aerobic anoxygenic photosynthetic bacteria (AAnP) were recently proposed to be significant contributors to global oceanic carbon and energy cycles. However, AAnP abundance, spatial distribution, diversity and potential ecological importance remain poorly understood. Here we present metagenomic data from the Global Ocean Sampling expedition indicating that AAnP diversity and abundance vary in different oceanic regions. Furthermore, we show for the first time that the composition of AAnP assemblages change between different oceanic regions, with specific bacterial assemblages adapted to open ocean or coastal areas respectively. Our results support the notion that marine AAnP populations are complex and dynamic, and compose an important fraction of bacterioplankton assemblages in certain oceanic areas.

Evidence for the ubiquity of mixotrophic bacteria in the upper ocean: implications and consequences.

Microorganisms are usually grouped into those relying solely on harvesting light (phototrophy) or those relying solely on the assimilation of organic or inorganic compounds (chemotrophy) to meet their requirements for energy. As a carbon source for biomass production, they can use either inorganic carbon (autotrophy) or organic substances (heterotrophy) (Table ​(Table1).1). Most biogeochemical studies of marine environments use the dichotomy of grouping microorganisms into photo(auto)trophs (primary producers like algae and cyanobacteria) and (organo)heterotrophs (secondary producers, like most heterotrophic bacteria) (see, for example, references 2 and 74). TABLE 1. Definitions of metabolic strategies to obtain carbon and energya It is well known that metabolic modes of aquatic microorganisms are more diverse than that, and modes such as mixotrophy, chemoautotrophy, chemoheterotrophy, or photoheterotrophy do exist. For microeukaryotes, mixotrophy is a widespread phenomenon in aquatic habitats and is observed in many organisms (see, for example, references 16, 62, 82, and 83). Some Bacteria, like purple nonsulfur bacteria (anoxygenic photosynthetic bacteria), are also able to alter between photo-, hetero-, auto-, litho-, and organotrophy, depending on the environmental conditions (93). Although mixotrophic bacteria, which invest in both phototrophic and heterotrophic enzymatic apparatuses and combine them with autotrophic and/or organotrophic strategies, have been isolated from various aquatic environments (see, for example, references 66, 75, and 93), their contribution to total biomass and their importance for biogeochemical processes in aquatic systems have been ignored. However, recent genome data of two Prochlorococcus strains (67) and one Synechococcus strain (56), together with results from isotope tracer uptake experiments (45, 97, 98), suggest that at least certain strains of these ubiquitous picocyanobacteria are not pure photoautotrophs and can take up organic compounds. Cyanobacteria are not the only bacteria that can harvest light energy. Aerobic anoxygenic photosynthetic bacteria (AAnPB) use mainly bacteriochlorophyll a (Bchl-a) for photosynthesis (for example, see references 75 and 93), whereas other bacteria can use proteorhodopsin, a light-driven proton pump (3, 13, 17, 23). Isolated representatives of these bacteria usually use organic carbon for cell synthesis and are characterized as photo(organo)heterotrophs (22-24, 63, 93). Genetic community surveys suggest that AAnPB and proteorhodopsin-containing bacteria (PRB) are common in surface waters throughout the oceans of the world and can make up a substantial fraction of the bacterial community in oligotrophic marine environments (see, for example, references 3-5, 10, 34, 35, 69-72, 80, and 89). Furthermore, it has been shown that phylogenetic clades, including organisms with photoreceptors, can be significant in degradation processes of organic compounds (43-45). These observations suggest that mixotrophic bacteria may be major players in photo-, hetero-, auto-, and organotrophic processes in the upper ocean, which may demand a thorough revision of our understanding of how microorganisms contribute to biogeochemical cycles in the marine environment.

Influence of photoperiod on pigmentation and metabolic efficiency of the marine aerobic anoxygenic photosynthetic bacterium Erythrobacter longus Strain NJ3Y

The marine photoheterotroph Erythrobacter longus Strain NJ3Y was grown in continuous culture under variable light:dark (L:D) regimes of 24:0, 12:12 and 0:24 h to examine the influence of photoperiod on pigmentation and metabolic efficiency. Average carbon mass balances for each light regime closed to within 5 %, giving confidence in the measured variables as well as calculations of physiological parameters. Significant differences in photosynthetic pigmentation were observed for the experimental light treatments, with highest and lowest pigment concentrations measured in the 0:24 and 24:0 h L:D regimes, respectively, indicating that the photosynthetic pigments of E. longus Strain NJ3Y are preferentially synthesized in the dark. These differences are consistent with the strategy that photosynthetic pigments are produced during periods of darkness, for use in energy harvesting during subsequent light periods. In contrast, concentrations of the photoprotective pigment caloxanthin sulfate were highest for cells grown under a 12:12 h L:D cycle, indicating that this carotenoid is synthesized in the light and the dark. It is concluded that the 12:12 h L:D regime provides the maximum opportunity for E. longus Strain NJ3Y to derive a metabolic advantage from light availability (i.e. by enabling it to both synthesize and utilize its light harvesting apparatus). The corresponding carbon-specific glucose uptake rate was similar to 30% higher than that measured for the 0:24 and 24:0 h L:D regimes. It is hypothesized that light-stimulated rates of dissolved organic carbon uptake by bacteriochlorophyll a containing bacteria confer a slight competitive advantage over bacteria that lack this photosynthetic machinery. Lowest glucose-specific biomass yields (Y-x/s, g dry cell wt g(-1) glucose) were observed for the 12:12 h L:D treatment, suggesting that under the culture conditions used in this study, photosynthesis does not contribute significantly to the growth of E. longus Strain NJ3Y.

Growth and bacteriochlorophyll a formation in taxonomically diverse aerobic anoxygenic phototrophic bacteria in chemostat culture: Influence of light regimen and starvation

The influence of light and starvation on bacteriochlorophyll a (bchl a) and biomass formation of some aerobic anoxygenic photosynthetic bacteria was investigated in chemostat culture. Three species recently isolated from dinoflagellate cultures were compared, Dinoroseobacter shibae, which contained relatively high amounts of bchl a, and Stappia sp. DFL-11 and Hoeflea phototrophica, which both have very low amounts of photosynthetic pigments. Simulating day/night alternation D. shibae was subjected to 7 light:dark cycles = 8 h:16 h and 3 light:dark cycles = 16 h:8 h. Using a dilution rate of 0.1 h −1 and succinate as a substrate (8.5 mmol/l) the concentration of bchl a decreased during the light period due to inhibition by light and recovered always to about the previous level during the dark period. Biomass increased during the light period showing that additional energy was generated in the light. Nutrient deficiency in the absence or presence of light was studied by exposing continuous cultures growing in the dark under the conditions described above to 8 h of illumination, starvation, i.e. interruption of medium supply, or both. The cultures of D. shibae exhibited a bchl a base level of 2.5 nmol/mg protein, which decreased reversibly in the light and increased significantly during starvation in the dark to reach a level of 4 nmol/mg protein 16 h after medium supply was resumed, indicating a slow regulatory response towards periodic starvation in D. shibae. Under simultaneous illumination and starvation conditions, these two effects apparently cancelled one another out, resulting in unchanged levels of bchl a. By contrast, the cultures of Stappia sp. and H. phototropica were characterized by bchl a contents of almost zero in the dark, little change under illumination or starvation, but a very marked increase after simultaneous illumination and starvation, reaching 0.16 and 0.24 nmol bchl a/mg protein, respectively, 16 h after medium supply was resumed. These data suggest the presence of a regulatory mechanism integrating light stimuli and starvation related metabolic signals. The different physiological behaviour of the two groups is discussed in terms of the significance of aerobic anoxygenic photosynthesis in their natural environment.

Aerobic anoxygenic photosynthesis genes and operons in uncultured bacteria in the Delaware River

Photosynthesis genes and operons of aerobic anoxygenic photosynthetic (AAP) bacteria have been examined in a variety of marine habitats, but genomic information about freshwater AAP bacteria is lacking. The goal of this study was to examine photosynthesis genes of AAP bacteria in the Delaware River. In a fosmid library, we found two clones bearing photosynthesis gene clusters with unique gene content and organization. Both clones contained 37 open reading frames, with most of those genes encoding known AAP bacterial proteins. The genes in one fosmid were most closely related to those of AAP bacteria in the Rhodobacter genus. The genes of the other clone were related to those of freshwater beta-proteobacteria. Both clones contained the acsF gene, which is required for aerobic bacteriochlorophyll synthesis, suggesting that these bacteria are not anaerobes. The beta-proteobacterial fosmid has the puf operon B-A-L-M-C and is the first example of an uncultured bacterium with this operon structure. The alpha-3-proteobacterial fosmid has a rare gene order (Q-B-A-L-M-X), previously observed only in the Rhodobacter genus. Phylogenetic analyses of photosynthesis genes revealed a possible freshwater cluster of AAP beta-proteobacteria. The data from both Delaware River clones suggest there are groups of freshwater or estuarine AAP bacteria distinct from those found in marine environments.

Putative novel photosynthetic reaction centre organizations in marine aerobic anoxygenic photosynthetic bacteria: insights from metagenomics and environmental genomics

Photosynthetic core complexes of anoxygenic bacteria consist of reaction centres (RCs) surrounded by light-harvesting complexes (LHC). The structural proteins of the RC-LHC1 complex are encoded by the puf-operon. We find diverse operon organizations of puf-operons that reflect structural differences of the core complex in marine aerobic anoxygenic photosynthetic bacteria (AAnP). By analysis of environmental DNA records coming from AAnP bacteria we find several unknown proteins downstream to the pufM, which were assigned as novel PufX proteins. As all known pufX genes belong to Rhodobacter strains which carry out anaerobic photosynthesis, this may be the first observation of a PufX-containing RCs in aerobic anoxygenic photosynthetic bacteria. Phylogenetic analyses of PufM proteins from cultured as well as from uncultured bacteria show that PufM from operons containing putative novel pufX genes are grouped with Rhodobacter and not with Roseobacter strains.

Potential contribution of aerobic anoxygenic photosynthetic bacteria to marine carbon cycle

Potential contribution of aerobic anoxygenic photosynthetic bacteria to marine carbon cycle