Search Results (45)

Rhodopseudomonas is recognized for its versatile metabolic capabilities that enable it to effectively degrade pollutants and survive various environmental stresses. In this study, we conducted a genome analysis of Rhodopseudomonas sp. P1 to investigate its genetic potential for wastewater treatment processes. Phylogenetic and genome-relatedness analyses confirmed that strain P1 is genetically distinct from other species within the Rhodopseudomonas genus, establishing it as a novel species. The genome sequences obtained and analyzed focused on genes related to carbon and nutrient removal, photosynthetic capabilities, nitrate and nitrite reduction, and the biodegradation of common wastewater pollutants. The identification of wastewater treatment-related genes followed an extensive review of the existing literature that helped in selecting genes involved in various wastewater treatment mechanisms. The genome of Rhodopseudomonas sp. P1 contains a diverse array of genes involved in carbon and nutrient cycling, pollutant biodegradation, and metal resistance, all of which are crucial for its survival in the complex wastewater environment. Specifically, the strain contains genes responsible for the denitrification, nitrogen fixation, sulfur cycling, and detoxification of toxic metals such as copper and arsenic. These findings highlight the potential application of Rhodopseudomonas sp. P1 in wastewater treatment, particularly in environments contaminated with organic pollutants and heavy metals. However, while the genomic features indicate significant promise, the practical implementation of Rhodopseudomonas sp. P1 in real-world wastewater treatment systems will require further investigation, optimization, and validation to fully harness its potential for sustainable and efficient wastewater treatment. Full article

This study explores the valorization of bread waste for poly-β-hydroxybutyrate (PHB) production through a combined dark fermentation (DF) and photofermentation (PF) process. DF, performed using Lactobacillus amylovorus DSM 20532, efficiently converted bread waste into a lactate- and acetate-rich substrate within 120 h. The resulting fermented bread broth (FBB) was enriched with essential nutrients by adding digestate from anaerobic digestion, replacing the need for chemical supplements. Six purple non-sulfur bacteria (PNSB) strains were screened for PHB production in the FBB. Cereibacter johrii Pisa7 demonstrated the highest PHB accumulation (50.73% w PHB/w cells), and biomass increase (+1.26 g L⁻¹) over 336 h, leading to its selection for scale-up. Scale-up experiments were conducted in a 5 L photobioreactor with LED lights optimized for PNSB growth. C. johrii Pisa7 accumulated PHB at 15.17% and 11.51% w PHB/w cells in two independent trials, corresponding to productivities of 2.03 and 0.89 mg PHB L⁻¹ h⁻¹. These results confirm the scalability of the process while maintaining competitive PHB yields. This study highlights the potential of bread waste as a low-cost carbon source for bioplastic production, contributing to a circular bioeconomy by converting food waste into sustainable materials. Full article

Hydrogen (H₂) production by photosynthetic microorganisms is a viable option for renewable energy due to its sustainability and potential for widespread application. Green algae, cyanobacteria, and purple non-sulfur bacteria have shown great promise in bio-H₂ production. However, problems such as low H₂ production rates and high H₂ production costs continue to hinder the commercial scalability of these systems. To overcome these obstacles, genetic engineering selection of robust strains capable of coping with variable environmental conditions, optimization of growth conditions, use of wastewater, and biotechnological approaches such as immobilization are carefully considered. The aim of this review is to provide a thorough overview of the methods and developments that can improve H₂ production and to highlight current difficulties and future directions for further studies. Full article

The overuse of chemical fertilizers under adverse conditions endangers the sustainability of agriculture. A biological approach should be investigated to address this issue. Therefore, this study aimed to detect the potency of purple non-sulfur bacteria that can fix nitrogen (N) (PNSB-fN) Rhodobacter sphaeroides in soil N fertility, plant N uptake, growth, and rice yield. In brief, an experiment was conducted to check whether the biofertilizer containing PNSB-fN strains can improve rice yield and soil fertility under a highly saline acidic condition. A randomized complete block design was used with four replicates on saline soil in An Bien-Kien Giang, Vietnam. The first factor was the N fertilizer level, i.e., (i) 100%, (ii) 75%, (iii) 50%, and (iv) 0%; the second factor was the PNSB-fN (R. sphaeroides), i.e., (i) the control, (ii) S01, (iii) S06, and (iv) combined S01–S06. In the results, supplying PNSB-fN increased NH₄⁺ compared with the control, i.e., 104.7–112.0 mg NH₄⁺ kg⁻¹ compared with 94.0 mg NH₄⁺ kg⁻¹ in season 1 and 35.9–38.0 mg NH₄⁺ kg⁻¹ compared with 34.2 mg NH₄⁺ kg⁻¹ in season 2. Additionally, by supplying each PNSB-fN strain, the soil Na⁺ and plant Na in culm leaf and grain were decreased in comparison with those in treatments without PNSB-fN. The total N uptake was also enhanced by the PNSB-fN compared with the control. Moreover, supplying PNSB-fN improved the crop height, panicle length, panicle quantity pot⁻¹, grain quantity panicle⁻¹, filled spikelet rate, and grain yield compared with the control. Ultimately, in extremely saline soil, the mixture of PNSB-fN not only improved soil fertility and reduced soil salinity but also replaced 25% of chemical N fertilizer to ensure sustainable agriculture. This newly developed biofertilizer was potent in not only improving the rice and soil health in the locality but also performing the same under similar conditions around the globe. Full article

Earlier, it has been shown that carotenoid-dependent singlet oxygen photogeneration in LH2 of Ectothiorhodospira haloalkaliphila leads to damage to pigments and protein. Present work continues this investigation using LH2 complexes with altered carotenoid composition: carotenoid-less LH2, and LH2 complexes with incorporated neurosporene, spheroidene, or rhodopin (LH2-Neu, LH2-Sph, or LH2-Rho, respectively). This work provides the first data on the products (hydroperoxides of organic molecules, most likely components of the protein matrix of the complexes) of the interaction of singlet oxygen with LH2 components with a modified carotenoid composition; the ability of various carotenoids to both influence the stability of LH2 and participate in oxidative damage to the complexes is assessed. It was shown that inhibition of carotenoid synthesis led to a decrease in LH2 thermal stability and reduced the light-induced oxidative damage to bacteriochlorophyll and protein. Re-incorporation of exogenous carotenoids did not return stability of the complexes but reduced the tendency of complexes to aggregate, and (in the case of LH2-Rho) reactivated both photooxidation of bacteriochlorophyll and photoproduction of organic hydroperoxides. It was concluded that carotenoids play an important role in comple x stability and are capable of inducing oxidative damage to LH2 components through singlet oxygen photogeneration. Full article

The genome of the mildly thermophilic hot spring purple sulfur bacterium, Allochromatium (Alc.) tepidum, contains a multigene pufBA family that encodes a series of α- and β-polypeptides, collectively forming a heterogeneous light-harvesting 1 (LH1) complex. The Alc. tepidum LH1, therefore, offers a unique model for studying an intermediate phenotype between phototrophic thermophilic and mesophilic bacteria, particularly regarding their LH1 Qy transition and moderately enhanced thermal stability. Of the 16 α-polypeptides in the Alc. tepidum LH1, six α1 bind Ca²⁺ to connect with β1- or β3-polypeptides in specific Ca²⁺-binding sites. Here, we use the purple bacterium Rhodospirillum rubrum strain H2 as a host to express Ca²⁺-bound and Ca²⁺-free Alc. tepidum LH1-only complexes composed of α- and β-polypeptides that either contain or lack the calcium-binding motif WxxDxI; purified preparations of each complex were then used to test how Ca²⁺ affects their thermostability and spectral features. The cryo-EM structures of both complexes were closed circular rings consisting of 14 αβ-polypeptides. The Q_y absorption maximum of Ca²⁺-bound LH1 (α1/β1 and α1/β3) was at 894 nm, while that of Ca²⁺-free (α2/β1) was at 888 nm, indicating that Ca²⁺ imparts a Q_y transition of 6 nm. Crucially for the ecological success of Alc. tepidum, Ca²⁺-bound LH1 complexes were more thermostable than Ca²⁺-free complexes, indicating that calcium plays at least two major roles in photosynthesis by Alc. tepidum—improving photocomplex stability and modifying its spectrum. Full article

The genus Skermanella comprises important soil bacteria that are often associated with the crop rhizospheres, but its physiological traits remain poorly understood. This study characterizes Skermanella sp. TT6^T, isolated from human skin, with a focus on its metabolic and environmental adaptations. Genome sequencing and phylogenomic analyses revealed that the strain TT6^T is most closely related to S. rosea M1^T, with average nucleotide identity and digital DNA–DNA hybridization values of 94.14% (±0.5%) and 64.7%, respectively. Comparative genomic analysis showed that the strains TT6^T, S. rosea M1^T and S. mucosa 8-14-6^T share the Calvin cycle, and possess photosynthetic genes associated with the purple bacteria-type photosystem II. The strains TT6^T and S. rosea M1^T exhibited growth in a nitrogen-free medium under microaerobic conditions, which were generated in test tubes containing 0.1% soft agar. Under these conditions, with nitrate as a nitrogen source, S. rosea M1^T formed gases, indicating denitrification. Strain TT6^T also contains gene clusters involved in trehalose and carotenoid biosynthesis, along with salt-dependent colony morphology changes, highlighting its adaptive versatility. Genomic analyses further identified pathways related to hydrogenase and sulfur oxidation. Phenotypic and chemotaxonomic traits of strain TT6^T were also compared with closely related type strains, confirming its genotypic and phenotypic distinctiveness. The new species, Skermanella cutis sp. nov., is proposed, with TT6^T (=KCTC 82306^T = JCM 34945^T) as the type strain. This study underscores the agricultural and ecological significance of the genus Skermanella. Full article

Marshes are an important ecosystem, acting as a biodiversity hotspot, a carbon sink and a bioremediation site, breaking down anthropogenic waste such as antibiotics, metals and fertilizers. Due to their participation in these metabolic activities and their capability to contribute to primary productivity, the microorganisms in such habitats have become of interest to investigate. Since Proteobacteria were previously found to be abundant and the waters are well aerated and organic-rich, this study on the presence of anoxygenic phototrophic bacteria, purple non-sulfur bacteria and aerobic anoxygenic phototrophs in marshes was initiated. One sample was collected at each of the seven Manitoban sites, and anoxygenic phototrophs were cultivated and enumerated. A group of 14 strains, which represented the phylogenetic diversity of the isolates, was physiologically investigated further. Aerobic anoxygenic phototrophs and purple non-sulfur bacteria were present at each location, and they belonged to the α- and β-Proteobacteria subphyla. Some were closely related to known heavy metal reducers (Brevundimonas) and xenobiotic decomposers (Novosphingobium and Sphingomonas). All were able to synthesize the photosynthetic complexes aerobically. This research highlights the diversity of and the potential contributions that anoxygenic phototrophs make to the essential functions taking place in wetlands. Full article

Using beneficial microorganisms, such as purple non-sulfur bacteria (PNSB), has shown enormous potential for improving plant growth and agricultural production. However, the full extent of their benefits and interactions with agricultural practices is yet to be fully understood. The present study aimed to investigate the use of PNSB in crop rotation practice, focusing on its impact on rice growth and yield. The experiment was conducted over two rice cropping seasons, with djulis grown between the rice as a rotation crop. The study shows that PNSB treatment increased the concentration of 5-aminolevulinic acid (5-ALA) in plants, indicating enhanced photosynthesis. Moreover, when combined with crop rotation, PNSB remarkably improved soil fertility. These combined benefits resulted in substantial increases in tiller numbers (163%), leaf chlorophyll content (13%), and lodging resistance (66%), compared to the untreated plants. The combined treatment also resulted in higher productive tillers per hill (112%), average grain per hill (65%), and grain fertility (26%). This led to increased grain yield (65%), shoot dry weight (15%), and harvest index (37%). The findings clearly suggest that the incorporation of PNSB in crop rotation strategies can significantly augment the growth and yield of rice crops. These insights, pivotal for sustainable rice cultivation, hold the potential to simultaneously tackle the pressing issues of global food security and climate change. Full article

Circadian rhythms, characterized by approximately 24 h cycles, play a pivotal role in enabling various organisms to synchronize their biological activities with daily variations. While ubiquitous in Eukaryotes, circadian clocks remain exclusively characterized in Cyanobacteria among Prokaryotes. These rhythms are regulated by a core oscillator, which is controlled by a cluster of three genes: kaiA, kaiB, and kaiC. Interestingly, recent studies revealed rhythmic activities, potentially tied to a circadian clock, in other Prokaryotes, including purple bacteria such as Rhodospirillum rubrum, known for its applications in fuel and plastic bioproduction. However, the pivotal question of how light and dark cycles influence protein dynamics and the expression of putative circadian clock genes remains unexplored in purple non-sulfur bacteria. Unraveling the regulation of these molecular clocks holds the key to unlocking optimal conditions for harnessing the biotechnological potential of R. rubrum. Understanding how its proteome responds to different light regimes—whether under continuous light or alternating light and dark cycles—could pave the way for precisely fine-tuning bioproduction processes. Here, we report for the first time the expressed proteome of R. rubrum grown under continuous light versus light and dark cycle conditions using a shotgun proteomic analysis. In addition, we measured the impact of light regimes on the expression of four putative circadian clock genes (kaiB1, kaiB2, kaiC1, kaiC2) at the transcriptional and translational levels using RT-qPCR and targeted proteomic (MRM-MS), respectively. The data revealed significant effects of light conditions on the overall differential regulation of the proteome, particularly during the early growth stages. Notably, several proteins were found to be differentially regulated during the light or dark period, thus impacting crucial biological processes such as energy conversion pathways and the general stress response. Furthermore, our study unveiled distinct regulation of the four kai genes at both the mRNA and protein levels in response to varying light conditions. Deciphering the impact of the diel cycle on purple bacteria not only enhances our understanding of their ecology but also holds promise for optimizing their applications in biotechnology, providing valuable insights into the origin and evolution of prokaryotic clock mechanisms. Full article

The purple sulfur bacterium Thiocapsa roseopersicina BBS is interesting from both fundamental and practical points of view. It possesses a thermostable HydSL hydrogenase, which is involved in the reaction of reversible hydrogen activation and a unique reaction of sulfur reduction to hydrogen sulfide. It is a very promising enzyme for enzymatic hydrogenase electrodes. There are speculations that HydSL hydrogenase of purple bacteria is closely related to sulfur metabolism, but confirmation is required. For that, the full genome sequence is necessary. Here, we sequenced and assembled the complete genome of this bacterium. The analysis of the obtained whole genome, through an integrative approach that comprised estimating the Average Nucleotide Identity (ANI) and digital DNA-DNA hybridization (DDH) parameters, allowed for validation of the systematic position of T. roseopersicina as T. bogorovii BBS. For the first time, we have assembled the whole genome of this typical strain of a new bacterial species and carried out its functional description against another purple sulfur bacterium: Allochromatium vinosum DSM 180T. We refined the automatic annotation of the whole genome of the bacteria T. bogorovii BBS and localized the genomic positions of several studied genes, including those involved in sulfur metabolism and genes encoding the enzymes required for the TCA and glyoxylate cycles and other central metabolic pathways. Eleven additional genes coding proteins involved in pigment biosynthesis was found. Full article

Photo-fermentation is an efficient hydrogen production pathway in which purple non-sulfur bacteria (PNSB) play an active role and produce hydrogen as a part of their metabolism under optimal conditions. These bacteria work under the influence of light to advance their metabolism and use various substrates, such as simple sugars and volatile fatty acids, to produce hydrogen. This article presents a comparative review of several bacterial strains that have been efficiently used to produce hydrogen by photo-fermentation under different optimized conditions, including the substrate, its concentration, type and capacity of the bioreactor, light sources and intensities, and process conditions to achieve the maximum biohydrogen production rate. The analysis showed that the Rhodopseudomonas palustris is the main bacterium used for hydrogen production, with a maximum hydrogen production rate of 3.2 mM/h using 27.8 mM of glucose in a 165 mL serum bottle and 3.23 mM/h using 50 mM of glycerol at pH 7, followed by Rhodobacter sphaeroides, which gave a hydrogen production rate as high as 8.7 mM/h, using 40 mM of lactic acid, pH 7, and 30 °C temperature in a single-walled glass bioreactor. However, it is not preferred over R. palustris due to its versatile metabolism and ability to use an alternative mode if the conditions are not carefully adjusted, which can be a problem in hydrogen production. Full article

The rates of oxygenic and anoxygenic photosynthesis, the microorganisms responsible for these processes, and the hydrochemical characteristics of the sulfide-containing karst lakes, Black Kichier and Big Kichier (Mari El Republic), were investigated. In these lakes, a plate of anoxygenic phototrophic bacteria (APB) is formed at the upper boundary of sulfide occurrence in the water. The phototrophic community of the chemocline zone was analyzed using a combination of high-throughput sequencing of the 16S rRNA gene fragments and light and electron microscopic techniques. Green-colored Chlorobium clathratiforme were absolutely predominant in both lakes. The minor components included green sulfur bacteria (GSB) Chlorobium spp., symbiotic consortia Chlorochromatium magnum and Pelochromatium roseum, purple sulfur bacteria (PSB) Chromatium okenii, and unidentified phylotypes of the family Chromatiaceae, as well as members of the Chloroflexota: Chloronema sp. and Oscillochloris sp. Based on the results of the molecular analysis, the taxonomic status of Ancalochloris perfilievii and other prosthecate GSB, as well as of the PSB Thiopedia rosea, which were visually revealed in the studied freshwater lakes, is discussed. Full article

Hydrogen (H₂) as a clean fuel holds global potential and can be produced through bio-processes. To enhance bioH₂ yields, integrated systems have been proposed, combining dark fermentation (DF) of wastewater with a subsequent photofermentation (PF) stage involving purple non-sulfur (PNS) bacteria. Mixed cultures of PNS bacteria and their microbial ecology have been relatively understudied despite the known benefits of mixed cultures in industrial applications. The aim of this study was to obtain various mixed cultures of PNS bacteria under different environmental conditions during the enrichment stage. Four different mixed cultures were obtained (A, B, C, and D). However, in the H₂ production phase, only Consortium A, which had been enriched with malic acid as the carbon source, exposed to 32 W m⁻² of irradiance, and subjected to intermittent agitation, produced H₂ with a yield of 9.37 mmol H₂ g⁻¹ COD. The consortia enriched were a hybrid of PF and DF bacteria. Especially in Consortium A, Rhodopseudomonas palustris was the dominant organism, and various DF bacteria were positively associated with H₂ production, with their dominance comparable to that of PNS bacteria. Despite the reported low yields, optimizing environmental conditions for this culture could potentially enhance hydrogen production from DF effluents. Full article

In the pursuit of cultivating anaerobic anoxygenic phototrophs with unusual absorbance spectra, a purple sulfur bacterium was isolated from the shoreline of Baltrum, a North Sea island of Germany. It was designated strain 970, due to a predominant light harvesting complex (LH) absorption maximum at 963–966 nm, which represents the furthest infrared-shift documented for such complexes containing bacteriochlorophyll a. A polyphasic approach to bacterial systematics was performed, comparing genomic, biochemical, and physiological properties. Strain 970 is related to Thiorhodovibrio winogradskyi DSM 6702^T by 26.5, 81.9, and 98.0% similarity via dDDH, ANI, and 16S rRNA gene comparisons, respectively. The photosynthetic properties of strain 970 were unlike other Thiorhodovibrio spp., which contained typical LH absorbing characteristics of 800–870 nm, as well as a newly discovered absorption band at 908 nm. Strain 970 also had a different photosynthetic operon composition. Upon genomic comparisons with the original Thiorhodovibrio strains DSM 6702^T and strain 06511, the latter was found to be divergent, with 25.3, 79.1, and 97.5% similarity via dDDH, ANI, and 16S rRNA gene homology to Trv. winogradskyi, respectively. Strain 06511 (=DSM 116345^T) is thereby described as Thiorhodovibrio litoralis sp. nov., and the unique strain 970 (=DSM 111777^T) as Thiorhodovibrio frisius sp. nov. Full article