Purple Non-sulfur Bacteria Research Articles

Usage of the Fungus Mucor indicus and the Bacterium Rhodovulum adriaticum in a Biorefinery System for Biochemical Production on Grass Hydrolysates

Utilization of various biomasses as raw materials in biorefineries represents a promising alternative for the production of valuable chemicals and biofuels. This study investigates the potential of the fungus Mucor indicus DSM 2158, cultivated on media containing the liquid phase of grass hydrolysates (LGH) and various nitrogen sources (yeast extract and corn steep liquor), for the production of valuable metabolites, such as ethanol, chitin, chitosan, and fatty acids. The ethanol yield varied depending on the cultivation media and conditions. The highest substrate-into-ethanol conversion coefficients (0.14–0.2 g g−1) were achieved during M. indicus cultivation on the LGH medium containing 5 g L−1 CSL in Erlenmeyer flasks and a bubble column bioreactor. In these cultivations, the highest fungal biomass concentrations (5.61–5.91 g L−1) were also observed. In flask cultivations, the highest content of total lipids in fungal dry biomass (15.76%) was observed. The obtained fungal biomass contained up to 22 fatty acids, with oleic acid (≈50%) being the most predominant. Chitin and chitosan yields were from 0.1 g g−1 to 0.3 g g−1 of dry biomass depending on the cultivation media and conditions. The residual media from the cultivation of M. indicus were used for the growth of the non-sulfur purple bacterium Rhodovulum adriaticum DSM 2781. Cultivations of R. adriaticum DSM 2781 on the residual media, in Erlenmeyer flasks and a stirred-tank bioreactor, resulted in a biomass yield of 0.50 to 2.26 g L−1. After extraction of bacterial biomass, total pigments (expressed as bacteriochlorophyll-a) were obtained in the range from 1.8 to 48.1 mg g−1 dry biomass depending on the media and cultivation conditions. The highest titer of bacteriochlorophyll-a was achieved during cultivation on the exhausted LGH medium with 5 g L−1 yeast extract. The established biorefinery system has to be optimized in order to reach capacity for transfer to a larger scale.

Genomic highlights of the phylogenetically unique halophilic purple nonsulfur bacterium, Rhodothalassium salexigens

Rhodothalassium (Rts.) salexigens is a halophilic purple nonsulfur bacterium and the sole species in the genus Rhodothalassium, which is itself the sole genus in the family Rhodothalassiaceae and sole family in the order Rhodothalassiales (class Alphaproteobacteria). The genome of this phylogenetically unique phototroph comprises 3.35 Mb and is highly chimeric, with nearly half of its genes originating from families other than the Rhodothalassiaceae, many of which lack phototrophic species. Photosynthesis genes in Rts. salexigens are not arranged in a typical photosynthesis gene cluster but are scattered across the genome, suggesting an origin from horizontal transfers. Despite an encoded RuBisCO, autotrophy has not been observed in Rts. salexigens, and enzymes that oxidize common inorganic electron donors are not encoded. Phospholipid biosynthesis in Rts. salexigens is restricted, and phosphoglycerolipids are the only phospholipids present in its intracytoplasmic membranes. Rts. salexigens fixes nitrogen using a Mo-containing nitrogenase and uses ammonia despite previous results that indicated it was a glutamate auxotroph. Glycine betaine is the sole osmolyte in Rts. salexigens, and enzymes are encoded that facilitate both its uptake and its biosynthesis from glycine. The genomic data also support chemotactic swimming motility, growth over a range of salinities, and the production of membrane-strengthening hopanoids.

Simultaneous Production of Hydrophobic Bioactive Compounds from Biomass of Purple Non-sulfur Bacterium Cereibacter sphaeroides

Simultaneous Production of Hydrophobic Bioactive Compounds from Biomass of Purple Non-sulfur Bacterium Cereibacter sphaeroides

Harnessing pH and light cycles to boost microbial protein production in mixed culture purple non-sulfur bacteria wastewater bioremediation

Harnessing pH and light cycles to boost microbial protein production in mixed culture purple non-sulfur bacteria wastewater bioremediation

Purple non-sulfur bacteria for biotechnological applications.

Purple non-sulfur bacteria are utilized for a range of biotechnological applications, including the production of bio-energy, single cell protein, fertilizer, bioplastics, fine chemicals, in wastewater treatment and in novel applications like co-cultures and microbial electrosynthesis.

Near-atomic cryo-EM structure of the light-harvesting complex LH2 from the sulfur purple bacterium Ectothiorhodospira haloalkaliphila.

Bacteria with the simplest system for solar energy absorption and conversion use various types of light-harvesting complexes for these purposes. Light-harvesting complex 2 (LH2), an important component of the bacterial photosynthetic apparatus, has been structurally well characterized among purple non-sulfur bacteria. In contrast, so far only one high-resolution LH2 structure from sulfur bacteria is known. Here, we report the near-atomic resolution cryoelectron microscopy (cryo-EM) structure of the LH2 complex from the purple sulfur bacterium Ectothiorhodospira haloalkaliphila, which allowed us to determine the predominant polypeptide composition of this complex and the identification of the most probable type of its carotenoid. Comparison of our structure with the only known LH2 complex from a sulfur bacterium revealed severe differences in the overall ring-like organization. Expanding the architectural universe of bacterial light-harvesting complexes, our results demonstrate that, as observed for non-sulfur bacteria, the LH2 complexes of sulfur bacteria may also exhibit various types of spatial organization.

Functional microorganisms in hydrogen production: Mechanisms and applications.

The rapid growth of global energy demand accelerates the development of sustainable, clean, and renewable energy sources. Biohydrogen production, driven by functional microorganisms, offers a promising solution. Multiple species of bacteria, fungi, microalgae, and archaea were able to produce hydrogen. This study reviewed the typical strains, together with their hydrogen-production mechanisms, e.g., bio-photolysis, photo fermentation, and dark fermentation. Bacteria (e.g., purple non-sulfur bacteria) and microalgae (e.g., cyanobacteria) have been widely investigated, with respect to the limited fungi and archaea. It showed that temperature, pH, and substrate availability could all substantially influence the efficiency of biohydrogen production. Meanwhile, photo and dark fermentations are favored for future possible industrial applications. Furthermore, this review summarized practical applications of biohydrogen production, such as utilization of bioreactors, waste treatment, and integrated systems for hydrogen production, highlighting the importance of functional microorganisms in advancing biohydrogen technology under global energy crisis.

Use of Nitrogen Fixing Purple Nonsulfur Bacteria to Produce Available Nitrogen for Rice (Oryza sativa L.) Cultivated in Saline Acidic Soil

This research aimed to select N2-fixation purple nonsulfur bacteria (PNSB) from saline acidic soils (SAS) in rice-shrimp system to enhance rice growth and yield. Two PNSB with highest nitrogen-releasing strains Luteovulum sphaeroides S01 and S06 were used, and the SAS was collected from Hong Dan and Thanh Phu districts. The 4 × 4 factorial experiment was carried out in a completely randomized block design, including a main factor as the liquid biofertilizers and the minor factor as the N fertilizer levels, with four replicates in a greenhouse. Both individual and mixed PNSB liquid biofertilizers significantly increased pH value and NH4 + content and reduced the exchangeable Na+ in both SAS sites. This led to 24.8–113.2% higher N uptake in rice and 6.48–30.5% lower Na accumulation in straw and 16.3–47.6% Na in grain. These results were considered as an evidence to improve rice grain yield by 27.5–56.6%. The L. sphaeroides S01 and S06 was greatly suitable for using as a biofertilizer for rice under saline acidic conditions.

Characterization of Novel Species of Potassium-Dissolving Purple Nonsulfur Bacteria Isolated from In-Dyked Alluvial Upland Soil for Maize Cultivation.

Potassium (K) is immobilized within the clay minerals, making it unavailable for plant use. Therefore, the current study aimed to (i) select isolates of purple nonsulfur bacteria that can dissolve K (K-PNSB) and (ii) evaluate the production of plant-growth-promoting substances by the K-PNSB isolates. The results revealed that from in-dyked alluvial soils in hybrid maize fields, 61 K-PNSB isolates were obtained under the pH 5.50 conditions. The total dissolved K content (Kdis) by the 61 K-PNSB isolates fluctuated from 56.2 to 98.6 mg L-1. Therein, three isolates, including M-Sl-09, M-So-11, and M-So-14 had Kdis of 48.1-48.8 mg L-1 under aerobic dark condition (ADC) and 47.6-49.7 mg L-1 under microaerobic light condition (MLC). Moreover, these three isolates can also fix nitrogen (19.1-21.5 mg L-1 and 2.64-7.24 mg L-1), solubilize Ca-P (44.3-46.8 mg L-1 and 0.737-6.965 mg L-1), produce indole-3-acetic acid (5.34-7.13 and 2.40-3.23 mg L-1), 5-aminolevulinic acid (1.85-2.39 and 1.53-2.47 mg L-1), siderophores (1.06-1.52 and 0.92-1.26 mg L-1), and exopolymeric substances (18.1-18.8 and 52.0-56.0%), respectively, under ADC and MLC. The bacteria were identified according to their 16S rDNA as Cereibacter sphaeroides M-Sl-09, Rhodopseudomonas thermotolerans M-So-11, and Rhodospeudomonas palustris M-So-14. These potential bacteria should be further investigated as a plant-growth-promoting biofertilizer.

Intact photosynthetic bacteria-based electrodes for self-powered metal ions monitoring

The low-cost and early monitoring of metal ion contaminants is paramount to prevent widespread contamination of water environments. Self-powered microbial electrochemical sensors represent an interesting approach to achieving this goal. Purple non-sulfur bacteria have a versatile metabolism and a well-characterized photosynthetic system, making them an ideal candidate for developing biohybrid technologies. In this work, we report the use of these bacteria in biophotoelectrodes to develop self-powered monitoring systems for two common pollutants, NiCl2 and CuSO4. The microbial biophotoelectrode was obtained on a homemade poly-hydroxybutyrate-carbon nanofibers electrode modified with a redox-adhesive polydopamine matrix-based entrapping the purple bacterium Rhodobacter capsulatus. The presence of 500 μM NiCl2 resulted in a 60 % decrease in current density, while the simultaneous presence of 100 μM NiCl2 and 100 mM CuSO4 led to an 83 % current inhibition. Given the implementation of the biophotoelectrode in the field, the biohybrid system was tested in a complex matrix containing beer, demonstrating the promising ability of the photoelectrochemical system to act as an efficient biosensor in complex solutions. Finally, the biohybrid electrode was coupled to a cathode performing oxygen reduction, which allowed obtaining a self-powered monitoring system, paving the way for the future implementation of a low-cost monitoring system for widespread metal ions contaminant monitoring.

Inhibition of phototrophic iron oxidation by nitric oxide in ferruginous environments

Anoxygenic phototrophic Fe(II) oxidizers (photoferrotrophs) are thought to have thrived in Earth’s ancient ferruginous oceans and played a primary role in the precipitation of Archaean and Palaeoproterozoic (3.8–1.85-billion-year-old) banded iron formations (BIFs). The end of BIF deposition by photoferrotrophs has been interpreted as the result of a deepening of water-column oxygenation below the photic zone, concomitant with the proliferation of cyanobacteria. However, photoferrotrophs may have experienced competition from other anaerobic Fe(II)-oxidizing microorganisms, altering the formation mechanism of BIFs. Here we utilize microbial incubations to show that nitrate-reducing Fe(II) oxidizers metabolically outcompete photoferrotrophs for dissolved Fe(II). Moreover, both experiments and numerical modelling show that the nitrate-reducing Fe(II) oxidizers inhibit photoferrotrophy via the production of toxic intermediates. Four different photoferrotrophs, representing both green sulfur and purple non-sulfur bacteria, are susceptible to this toxic effect despite having genomic capabilities for nitric oxide detoxification. Indeed, despite nitric oxide detoxification mechanisms being ubiquitous in some groups of phototrophs at the genomic level (for example, Chlorobi and Cyanobacteria) it is likely that they would still be affected. We suggest that the production of reactive nitrogen species during nitrate-reducing Fe(II) oxidation in ferruginous environments may have inhibited the activity of photoferrotrophs in the ancient oceans and thus impeded their role in the precipitation of BIFs.

Recovery of purple non-sulfur bacteria-mediated single-cell protein from domestic wastewater in two-stage treatment using high rate digester and raceway pond

Wastewater resources can be used to produce microbial protein for animal feed or organic fertiliser, conserving food chain resources. This investigation hasemployed thefermented sewage to photoheterotrophically grown purple non-sulfur bacteria (PNSB) in a 2.5 m3 pilot-scaleraceway-pond with infrared light to produce proteinaceous biomass. Fermented sewage with synthetic media consisting of sodium acetate and propionic acids at a surface-to-volume (S/V) ratio of 10 m2/m3 removed 89%, 93%, and 81% of chemical oxygen demand, ammonium nitrogen, and orthophosphate, respectively; whereas respective removal in fermented sewage alone without synthetic media was 73%, 73%, and 72% during batch operation of 120 h. The biomass yield of 0.88–0.95 g CODbiomass /g CODremoved with protein content of 40.3 ± 0.3%–43.9 ± 0.2% w/w was obtained for fermented sewage with synthetic media. The results revealed enhanced possibility of scaling-up the raceway reactor to recover resources from municipal wastewater and enable simultaneous high-rate PNSB single-cell protein production.

Synergistic interplay of photobioreactor mixing and static mixer configuration on Rhodoseupdomonas palustris’s growth and biohydrogen production

Inducing light/dark (L/D) cycles through mixing or recirculating the media in a photobioreactor improves light utilization for biohydrogen production during photoferentation. However, the mutual shading effect is a key challenge for photofermentation using purple non-sulphur bacteria (PNSB). In this study, mixing was explored as a mitigating methodology through the investigation of three different static mixer configurations: concentric, spiral, and half-moon, across four laminar flowrates: 1.2 L/min, 0.71 L/min, 0.31 L/min and 0.15 L/min. At 0.15 L/min, the half-moon and spiral static mixers significantly improved specific and cumulative hydrogen production by 11.2-fold and 114 %, respectively. Also, recirculating the fluid via a peristaltic pump resulted in a significant shearing effect, impacting cell viability. Inducing L/D cycles via a static mixer was thus beneficial for hydrogen production over an increased flow rate. Additionally, biomass productivity increased by up to 70 %, reaching a cell dry weight of 7.0 g/L with the spiral static mixer configuration at 0.15 L/min flow rate. Interestingly, this study found that the static mixers only significantly increased specific hydrogen production and light conversion efficiency at the lowest flow rate of 0.15 L/min, beyond which they showed no significant improvement in biohydrogen production. This indicates that high L/D cycling frequencies are unnecessary to alleviate the mutual shading effect for R. palustris, which is advantageous for upscaling. These findings emphasise the potential of static mixers as an alternative to increase light conversion efficiency and industrial hydrogen production.

Evaluating bioproducts production in a purple phototrophic biofilm photobioreactor: Fuel-synthesis wastewater vs. simple substrates

This study evaluated the influence of different carbon sources on purple non-sulphur bacteria (PNSB) biofilm formation, and the production of polyhydroxybutyrate (PHB) and other value-added bio-products. Higher PNSB growth and biofilm formation were observed in fuel-synthesis wastewater (FSW), followed by acetate. Both FSW and acetate cultures contained a large proportion of Rhizobiales, while sugar substrates led to yeast enrichment. Protein contents reached 40–41 % for acetate, which is suitable for single cell protein (SCP) use. The maximum PHB content from the suspended and biofilm growth was obtained from glucose (18.1 ± 0.10 %, 12.9 ± 1.11 %), followed by FSW (14.9 ± 0.25 %, 11.2 ± 0.50 %). FSW showed the highest overall productivity for both protein and PHB. Pigment concentrations were low for all substrates. The study underscores substrate influence on microbial community and bioproducts potential. It highlights FSW as a promising substrate for PNSB, suggesting its treatment integration for resource recovery.

Overexpression of RuBisCO form I and II genes in Rhodopseudomonas palustris TIE-1 augments polyhydroxyalkanoate production heterotrophically and autotrophically.

With the rising demand for sustainable renewable resources, microorganisms capable of producing bioproducts such as bioplastics are attractive. While many bioproduction systems are well-studied in model organisms, investigating non-model organisms is essential to expand the field and utilize metabolically versatile strains. This investigation centers on Rhodopseudomonas palustris TIE-1, a purple non-sulfur bacterium capable of producing bioplastics. To increase bioplastic production, genes encoding the putative regulatory protein PhaR and the depolymerase PhaZ of the polyhydroxyalkanoate (PHA) biosynthesis pathway were deleted. Genes associated with pathways that might compete with PHA production, specifically those linked to glycogen production and nitrogen fixation, were deleted. Additionally, RuBisCO form I and II genes were integrated into TIE-1's genome by a phage integration system, developed in this study. Our results show that deletion of phaR increases PHA production when TIE-1 is grown photoheterotrophically with butyrate and ammonium chloride (NH4Cl). Mutants unable to produce glycogen or fix nitrogen show increased PHA production under photoautotrophic growth with hydrogen and NH4Cl. The most significant increase in PHA production was observed when RuBisCO form I and form I & II genes were overexpressed, five times under photoheterotrophy with butyrate, two times with hydrogen and NH4Cl, and two times under photoelectrotrophic growth with N2 . In summary, inserting copies of RuBisCO genes into the TIE-1 genome is a more effective strategy than deleting competing pathways to increase PHA production in TIE-1. The successful use of the phage integration system opens numerous opportunities for synthetic biology in TIE-1.IMPORTANCEOur planet has been burdened by pollution resulting from the extensive use of petroleum-derived plastics for the last few decades. Since the discovery of biodegradable plastic alternatives, concerted efforts have been made to enhance their bioproduction. The versatile microorganism Rhodopseudomonas palustris TIE-1 (TIE-1) stands out as a promising candidate for bioplastic synthesis, owing to its ability to use multiple electron sources, fix the greenhouse gas CO2, and use light as an energy source. Two categories of strains were meticulously designed from the TIE-1 wild-type to augment the production of polyhydroxyalkanoate (PHA), one such bioplastic produced. The first group includes mutants carrying a deletion of the phaR or phaZ genes in the PHA pathway, and those lacking potential competitive carbon and energy sinks to the PHA pathway (namely, glycogen biosynthesis and nitrogen fixation). The second group comprises TIE-1 strains that overexpress RuBisCO form I or form I & II genes inserted via a phage integration system. By studying numerous metabolic mutants and overexpression strains, we conclude that genetic modifications in the environmental microbe TIE-1 can improve PHA production. When combined with other approaches (such as reactor design, use of microbial consortia, and different feedstocks), genetic and metabolic manipulations of purple nonsulfur bacteria like TIE-1 are essential for replacing petroleum-derived plastics with biodegradable plastics like PHA.

The potential of phosphorus-solubilizing purple nonsulfur bacteria in agriculture: Present and future perspectives

Abstract Phosphorus (P) is one of the essential macronutrients for crops. It is present in soil in two forms: soluble and insoluble. However, plants cannot absorb the insoluble forms, including Al-P, Fe-P, and Ca-P; thus, the phosphorus use efficiency is reduced. Therefore, the biological approaches should focus more on sustainable agriculture to overcome this constraint. This article cites publications relating to the biological P solubilizer group of bacteria, which have a highly potential adaptation to many conditions in soils. Among the biological approaches, purple nonsulfur bacteria (PNSB) are a potent group of bacteria according to their adaptability in acidic, saline, and toxic conditions based on their mechanisms in producing exopolymeric substances and siderophores under such adverse environments like acid-sulfate and saline soils. PNSB can solubilize P in soil to have more P availability for soil microbes and plants. This particular group of bacteria has been widely applied in liquid and solid forms from agricultural waste to promote plant growth under submerged conditions. Moreover, this article summarized the P-solubilizing mechanisms of P-solubilizing bacteria and introduced future research perspectives on patterns of PNSB in aspects of nutrient-providing potency, plant growth-promoting capability, and biological control capacity. However, the specific mechanisms of P solubilization by PNSB have not been well documented since the P-solubilizing mechanisms have been investigated on general P-solubilizing bacteria. Thus, specific pathways and metabolites relating to the P-solubilizing PNSB should be investigated, and attention should be addressed to them soon.

The phototrophic purple non-sulfur bacteria Rhodomicrobium spp. are novel chassis for bioplastic production.

Petroleum-based plastics levy significant environmental and economic costs that can be alleviated with sustainably sourced, biodegradable, and bio-based polymers such as polyhydroxyalkanoates (PHAs). However, industrial-scale production of PHAs faces barriers stemming from insufficient product yields and high costs. To address these challenges, we must look beyond the current suite of microbes for PHA production and investigate non-model organisms with versatile metabolisms. In that vein, we assessed PHA production by the photosynthetic purple non-sulfur bacteria (PNSB) Rhodomicrobium vannielii and Rhodomicrobium udaipurense. We show that both species accumulate PHA across photo-heterotrophic, photo-hydrogenotrophic, photo-ferrotrophic, and photo-electrotrophic growth conditions, with either ammonium chloride (NH4Cl) or dinitrogen gas (N2) as nitrogen sources. Our data indicate that nitrogen source plays a significant role in dictating PHA synthesis, with N2 fixation promoting PHA production during photoheterotrophy and photoelectrotrophy but inhibiting production during photohydrogenotrophy and photoferrotrophy. We observed the highest PHA titres (up to 44.08 mg/L, or 43.61% cell dry weight) when cells were grown photoheterotrophically on sodium butyrate with N2, while production was at its lowest during photoelectrotrophy (as low as 0.04 mg/L, or 0.16% cell dry weight). We also find that photohydrogenotrophically grown cells supplemented with NH4Cl exhibit the highest electron yields - up to 58.89% - while photoheterotrophy demonstrated the lowest (0.27%-1.39%). Finally, we highlight superior electron conversion and PHA production compared to a related PNSB, Rhodopseudomonas palustris TIE-1. This study illustrates the value of studying non-model organisms like Rhodomicrobium for sustainable PHA production and indicates future directions for exploring PNSB metabolisms.

Fast development of purple nonsulfur bacteria (PNSB) in a bubble column photobioreactor: Influence of carbon source and dissolved O2 availability on wastewater treatment performance

Photobioreactors with purple nonsulfur bacteria (PNSB) constitute a promising technology for wastewater treatment, gas purification, and high value-added bioproducts. In this work, different operational strategies were tested to investigate their impacts on photobioreactor performance, biomass properties, and microbial community. It showed that the operational conditions significantly influence the performance and microbial composition of PNSB photobioreactors. Anaerobic conditions favored the dominance of Rhodopseudomonas spp. and moderate COD removal efficiency (36.7 %), while aerobic conditions significantly enhanced COD removal efficiency (91.7 %) but altered the microbial community composition from PNSB to aerobic heterotrophic microorganisms, such as Delftia sp. and Microbacterium sp.. The removal ratio of chemical oxygen demand (COD):N:P was 100:10:2 under anaerobic conditions with continuous CO2 supply, while it was 100:1:1 under aerobic conditions with continuous supply of a CO2/O2 mixture. Net CO2 removal efficiencies of 2.8 % and 5.4 % were recorded under anaerobic conditions with and without the addition of organic carbon, respectively. The outlet CO2 concentration showed that CO2 uptake occurred under dark and anaerobic conditions without organic carbon. The reduced production of extracellular polymeric substances (EPS) was observed after COD was removed from the influent, preventing granule formation.

The metabolic pathways of carbon assimilation and polyhydroxyalkanoate production by Rhodospirillum rubrum in response to different atmospheric fermentation.

The purple nonsulfur bacteria, Rhodospirillum rubrum, is recognized as a potential strain for PHAs bioindustrial processes since they can assimilate a broad range of carbon sources, such as syngas, to allow reduction of the production costs. In this study, we comparatively analyzed the biomass and PHA formation behaviors of R. rubrum under 100% CO and 50% CO gas atmosphere and found that pure CO promoted the PHA synthesis (PHA content up to 23.3% of the CDW). Hydrogen addition facilitated the uptake and utilization rates of CO and elevated 3-HV monomers content (molar proportion of 3-HV up to 9.2% in the presence of 50% H2). To elucidate the genetic events culminating in the CO assimilation process, we performed whole transcriptome analysis of R. rubrum grown under 100% CO or 50% CO using RNA sequencing. Transcriptomic analysis indicated different CO2 assimilation strategy was triggered by the presence of H2, where the CBB played a minor role. An increase in BCAA biosynthesis related gene abundance was observed under 50% CO condition. Furthermore, we detected the α-ketoglutarate (αKG) synthase, converting fumarate to αKG linked to the αKG-derived amino acids synthesis, and series of threonine-dependent isoleucine synthesis enzymes were significantly induced. Collectively, our results suggested that those amino acid synthesis pathways represented a key way for carbon assimilation and redox potential maintenance by R. rubrum growth under syngas condition, which could partly replace the PHA production and affect its monomer composition in copolymers. Finally, a fed-batch fermentation of the R. rubrum in a 3-l bioreactor was carried out and proved H2 addition indeed increased the PHA accumulation rate, yielding 20% ww-1 PHA production within six days.

Complete genome sequence of Cereibacter sphaeroides f. sp. denitrificans strain IL106.

Cereibacter sphaeroides is a non-sulfur purple bacterium, one of the most versatile and thoroughly studied species of its kind, can grow on a variety of compounds photoheterotrophically, and is often used in bioremediation. We present the complete genome of Cereibacter sphaeroides f. sp. denitrificans underscoring its unique features.