Response of Nitrosospira sp. Strain AF-Like Ammonia Oxidizers to Changes in Temperature, Soil Moisture Content, and Fertilizer Concentration

Very little is known regarding the ecology of Nitrosospira sp. strain AF-like bacteria, a unique group of ammonia oxidizers within the Betaproteobacteria. We studied the response of Nitrosospira sp. strain AF-like ammonia oxidizers to changing environmental conditions by applying molecular methods and physiological measurements to Californian grassland soil manipulated in the laboratory. This soil is naturally high in Nitrosospira sp. strain AF-like bacteria relative to the much-better-studied Nitrosospira multiformis-like ammonia-oxidizing bacteria. Increases in temperature, soil moisture, and fertilizer interacted to reduce the relative abundance of Nitrosospira sp. strain AF-like bacteria, although they remained numerically dominant. The overall abundance of ammonia-oxidizing bacteria increased with increasing soil moisture and decreased with increasing temperature. Potential nitrification activity was altered by interactions among temperature, soil moisture, and fertilizer, with activity tending to be higher when soil moisture and temperature were increased. The increase in potential nitrification activity with increased temperature was surprising, given that the overall abundance of ammonia-oxidizing bacteria decreased significantly under these conditions. This observation suggests that (i) Nitrosospira sp. strain AF-like bacteria may respond to increased temperature with an increase in activity, despite a decrease in abundance, or (ii) that potential nitrification activity in these soils may be due to organisms other than bacteria (e.g., archaeal ammonia oxidizers), at least under conditions of increased temperature.     

Determination of Total Protein Content of Bacterial Cells by SYPRO Staining and Flow Cytometry

An assay has been developed for measuring protein biomass of marine planktonic bacteria by flow cytometry. The method was calibrated by using five species of Bacteria (an Arcobacter sp., a Cytophaga sp., an Oceanospirillum sp., a Pseudoalteromonas sp., and a Vibrio sp.) recently isolated from seawater samples and grown in culture at different temperatures. The intensity of SYPRO-protein fluorescence of these bacteria strongly correlated with their total protein content, measured by the bicinchoninic acid method to be in the range of 60 to 330 fg of protein cell⁻¹ (r² = 0.93, n = 34). According to the calibration, the mean biomass of planktonic bacteria from the North Sea in August 1998 was 24 fg of protein cell⁻¹.     

Isolation and Presumptive Identification of Adherent Epithelial Bacteria (“Epimural” Bacteria) from the Ovine Rumen Wall

One hundred sixty-one strains of adherent bacteria were isolated under anaerobic conditions from four sites on the rumen epithelial surface of sheep fed hay or a hay-grain ration. Before isolation of bacteria, rumen tissue was washed six times in an anaerobic dilution solution, and viable bacteria suspended in the washings were counted. Calculation indicated that unattached bacteria would have been removed from the tissue by this procedure, but a slow and progressive release of attached bacteria also occurred. Nevertheless, a wide range of characteristic morphological types remained associated with the epithelium as demonstrated by scanning electron microscopy. Most of these types were represented among the isolates. Characterization and presumptive identification of the isolates showed that 95.0% belonged to previously described genera of functionally significant rumen bacteria, including Butyrivibrio sp. (31.1%), Bacteroides sp. (22.4%), Selenomonas ruminantium (9.9%), Succinivibrio dextrinosolvens (8.7%), Streptococcus bovis (8.1%), Propionibacterium sp. (4.3%), Treponema sp. (3.1%), and Eubacterium sp., Lachnospira multiparus, and Ruminococcus flavefaciens (2.5% each). Eight isolates (5.0%) were not identified. L. multiparus was recovered only from hay-fed animals; all other genera were obtained from animals fed either ration. All S. bovis strains and two strains each of Bacteroides sp. and Butyrivibrio sp. were aerotolerant; all other strains were strictly anaerobic. Bacteria representing the gram-positive, facultatively anaerobic flora associated with rumen wall tissue (R. J. Wallace, K.-J. Cheng, D. Dinsdale, and E. R. Ørskov, Nature (London) 279:424-426, 1979) were therefore not recovered by the techniques used; instead a different fraction of the adherent population was isolated. The term “epimural” is proposed to describe the flora associated with the rumen epithelium.     

The roots of the halophyte Salicornia brachiata are a source of new halotolerant diazotrophic bacteria with plant growth-promoting potential

Soil salinity is the major cause limiting plant productivity worldwide. Nitrogen-fixing bacteria were enriched and characterised from roots of Salicornia brachiata, an extreme halophyte which has substantial economic value as a bioresource of diverse and valuable products. Nitrogen-free semisolid NFb medium with malate as carbon source and up to 4% NaCl were used for enrichment and isolation of diazotrophic bacteria. The isolates were tested for plant growth-promoting traits and 16S rRNA, nifH and acdS genes were analysed. For selected strains, plant growth-promoting activities were tested in axenically grown Salicornia seedlings at different NaCl concentrations (0–0.5M). New halotolerant diazotrophic bacteria were isolated from roots of S. brachiata. The isolates were identified as Brachybacterium saurashtrense sp. nov., Zhihengliuella sp., Brevibacterium casei, Haererehalobacter sp., Halomonas sp., Vibrio sp., Cronobacter sakazakii, Pseudomonas spp., Rhizobium radiobacter, and Mesorhizobium sp. Nitrogen fixation as well as plant growth-promoting traits such as indole acetic acid (IAA) production, phosphate solubilisation, and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity were demonstrated. For Brachybacterium saurashtrense and Pseudomonas sp., significant plant growth-promoting activities were observed in Salicornia in salt stress conditions. Salicornia brachiata is a useful source of new halotolerant diazotrophic bacteria with plant growth-promoting potential.     

Complementary cooperation between two syntrophic bacteria in pesticide degradation

Interactions between microbial species, including competition and mutualism, influence the abundance and distribution of the related species. For example, metabolic cooperation among multiple bacteria plays a major role in the maintenance of consortia. This study aims to clarify how two bacterial species coexist in a syntrophic association involving the degradation of the pesticide fenitrothion. To elucidate essential mechanisms for maintaining a syntrophic association, we employed a mathematical model based on an experimental study, because experiment cannot elucidate various conditions for two bacterial coexistence. We isolated fenitrothion-degrading Sphingomonas sp. TFEE and its metabolite of 3-methyl-4-nitrophenol (3M4N)-degrading Burkholderia sp. MN1 from a fenitrothion-treated soil microcosm. Neither bacterium can completely degrade fenitrothion alone, but they can utilize the second intermediate, methylhydroquinone (MHQ). Burkholderia sp. MN1 excretes a portion of MHQ during the degradation of 3M4N, from which Sphingomonas sp. TFEE carries out degradation to obtain carbon and energy. Based on experimental findings, we developed mathematical models that represent the syntrophic association involving the two bacteria. We found that the two bacteria are characterized by the mutualistic degradation of fenitrothion. Dynamics of two bacteria are determined by the degree of cooperation between two bacteria (i.e., supply of 3M4N by Sphingomonas sp. TFEE and excretion of MHQ by Burkholderia sp. MN1) and the initial population sizes. The syntrophic association mediates the coexistence of the two bacteria under the possibility of resource competition for MHQ, and robustly facilitates the maintenance of ecosystem function in terms of degrading xenobiotics. Thus, the mathematical analysis and numerical computations based on the experiment indicate the key mechanisms for coexistence of Sphingomonas sp. TFEE and Burkholderia sp. MN1 in syntrophic association involving fenitrothion degradation.     

Symbiotic adaptation of bacteria in the gut of Reticulitermes speratus: Low endo-β-1,4-glucanase activity

The termite is a good model of symbiosis between microbes and hosts and possesses an effective cellulose digestive system. Oxygen-tolerant bacteria, such as Dyella sp., Chryseobacterium sp., and Bacillus sp., were isolated from Reticulitermes speratus gut. Notably, the endo-β-1,4-glucanase (EG) activity of all 16 strains of isolated bacteria was low. Due to the combined activity of EG from the termites and their symbiotic protozoa, the bacteria might not be compelled to express EG. This observation demonstrates how well intestinal bacteria have assimilated themselves into the efficient cellulose digestive systems of termites.     

Dominant phylotypes in the 16S rRNA gene clone libraries from bacterial mats of the Uzon caldera (Kamchatka,Russia) hydrothermal springs

In situ analysis of the 16S rRNA genes from bacterial mats of five hydrothermal springs (36–58°C) in the Uzon caldera (Kamchatka, Russia) was carried out using clone libraries. Eight clone libraries contained 18 dominant phylotypes (over 4–5%). In most clone libraries, the phylotype of the green sulfur bacterium Chlorobaculum sp. was among the dominant ones. The phylotypes of the green nonsulfur bacteria Chloroflexus and Roseiflexus and of purple nonsulfur bacteria Rhodoblastus, Rhodopseudomonas, and Rhodoferax were also among the dominant ones. Cyanobacteria were represented by one dominant phylotype in a single spring. Among nonphototrophic bacteria, the dominant phylotypes belonged to Sulfyrihydrogenibium sp., Geothrix sp., Acidobacterium sp., Meiothermus sp., Thiomonas sp., Thiofaba sp., and Spirochaeta sp. Three phylotypes were not identified at the genus level. Most genera of phototrophic and nonphototrophic organisms corresponding to the phylotypes from Uzon hydrotherms have been previously revealed in the hydrotherms of volcanically active regions of America, Asia, and Europe. These results indicate predominance of bacterial mats carrying out anaerobic photosynthesis in the hydrotherms of the Uzon caldera.     

Biofilm Interactions between Distinct Bacterial Genera Isolated from Drinking Water

In the environment, multiple microorganisms coexist as communities, competing for resources and often associated as biofilms. In this study, single- and dual-species biofilm formation by, and specific activities of, six heterotrophic intergeneric bacteria were determined using 96-well polystyrene plates over a 72-h period. These bacteria were isolated from drinking water and identified by partial 16S rRNA gene sequencing. A series of planktonic studies was also performed, assessing the bacterial growth rate, motility, and production of quorum-sensing inhibitors (QSI). This constituted an attempt to identify key attributes allowing bacteria to effectively interact and coexist in a drinking-water environment. We observed that in both pure and dual cultures, all of the isolates formed stable biofilms within 72 h, with specific metabolic activity decreasing, in most cases, with an increase in biofilm mass. The largest single- and dual-biofilm amounts were found for Methylobacterium sp. and the combination of Methylobacterium sp. and Mycobacterium mucogenicum, respectively. Evidences of microbial interactions in dual-biofilm formation, associated with appreciable biomass variation in comparison with single biofilms, were found for the following cases: synergy/cooperation between Sphingomonas capsulata and Burkholderia cepacia, S. capsulata and Staphylococcus sp., and B. cepacia and Acinetobacter calcoaceticus and antagonism between S. capsulata and M. mucogenicum, S. capsulata and A. calcoaceticus, and M. mucogenicum and Staphylococcus sp. A neutral interaction was found for Methylobacterium sp.-M. mucogenicum, S. capsulata-Staphylococcus sp., M. mucogenicum-A. calcoaceticus, and Methylobacterium sp.-A. calcoaceticus biofilms, since the resultant dual biofilms had a mass and specific metabolic activity similar to the average for each single biofilm. B. cepacia had the highest growth rate and motility and produced QSI. Other bacteria producing QSI were Methylobacterium sp., S. capsulata, and Staphylococcus sp. However, only for S. capsulata-M. mucogenicum, S. capsulata-A. calcoaceticus, and M. mucogenicum-Staphylococcus sp., dual-biofilm formation seems to be regulated by the QSI produced by S. capsulata and Staphylococcus sp. and by the increased growth rate of S. capsulata. The parameters assessed by planktonic studies did not allow prediction and generalization of the exact mechanism regulating dual-species biofilm formation between the drinking-water bacteria.     

Adhesive properties of predominant bacteria in raw cow’s milk to bovine mammary gland epithelial cells

Various bacteria have been found in raw cow’s milk, and identifying milk microflora and its functions is critical for maintaining cow health and farm hygiene. Although studies on pathogens and spoilage bacteria in milk have been widely reported, the relationship between milk bacteria, including nonpathogenic bacteria, and the bovine udder is poorly understood. We investigated milk microflora over 1 year using a culture-dependent method and culture-independent analysis by denaturing gradient gel electrophoresis. Among 240 isolates, Lactococcus lactis (81/240) was predominant. The predominant genera were Lactococcus, Stenotrophomonas, Microbacterium, Chryseobacterium, Serratia and Pseudomonas. Among seven strains belonging to these predominant genera, two strains of L. lactis (ssp. lactis and ssp. cremoris) exhibited the highest adherence to bovine mammary gland epithelial cells (BMECs) derived from the bovine udder; 3.4 % of the inoculated bacteria adhered to BMECs. This was followed by Serratia sp. (1.6 %), Microbacterium sp. (0.8 %), Stenotrophomonas maltophilia (0.5 %), Pseudomonas sp. (0.3 %) and Chryseobacterium sp. (0.1 %). The two L. lactis isolates exhibited higher adherence to BMECs than type strains and isolates of various origins.     

The Effects of Plant Growth Substances and Mixed Cultures on Growth and Metabolite Production of Green Algae Chlorella sp.: A Review

Recent interest in the use of microalgae for the production of biofuels and bioproducts has stimulated an interest in methods to enhance the growth rate of microalgae. This review examines past work involving the stimulation of Chlorella sp. growth and metabolite production by plant growth substances as well as by mixed cultures of Chlorella sp. with bacteria. Plant growth substances known to regulate Chlorella sp. growth and metabolite production include auxins, cytokinins, abscisic acid, polyamines, brassinosteroids, jasmonic acid, salicylic acid, and combinations of two or three of the aforementioned substances. Mixed cultures of bacteria are examined, including both natural bacteria–algae consortia and artificially induced symbioses. For natural consortia, commonly occurring bacterial species, including the genera Brevundimonas and Sphingomonas, are discussed. For artificially induced symbioses, the use of the nitrogen-fixing bacterium Azospirillum is examined in detail. In particular, a variety of studies have involved the coimmobilization of Chlorella sp. with Azospirillum sp. in alginate beads, with the goal of using the mixed culture to treat wastewater. In summary, the use of plant growth substances and mixed cultures provides two methods to increase the growth of Chlorella sp., whether for the production of lipids for biofuels, the production of bioproducts, the treatment of wastewater, or a variety of other reasons.     

Nodulation in black locust by the Gammaproteobacteria Pseudomonas sp. and the Betaproteobacteria Burkholderia sp.

Nodulation abilities of bacteria in the subclasses Gammaproteobacteria and Betaproteobacteria on black locust (Robinia pseudoacacia) were tested. Pseudomonas sp., Burkholderia sp., Klebsiella sp., and Paenibacillus sp. were isolated from surface-sterilized black locust nodules, but their nodulation ability is unknown. The aims of this study were to determine if these bacteria are symbiotic. The species and genera of the strains were determined by RFLP analysis and DNA sequencing of 16S rRNA gene. Inoculation tests and histological studies revealed that Pseudomonas sp. and Burkholderia sp. formed nodules on black locust and also developed differentiated nodule tissue. Furthermore, a phylogenetic analysis of nodA and a BLASTN analysis of the nodC, nifH, and nifHD genes revealed that these symbiotic genes of Pseudomonas sp. and Burkholderia sp. have high similarities with those of rhizobial species, indicating that the strains acquired the symbiotic genes from rhizobial species in the soil. Therefore, in an actual rhizosphere, bacterial diversity of nodulating legumes may be broader than expected in the Alpha-, Beta-, and Gammaproteobacteria subclasses. The results indicate the importance of horizontal gene transfer for establishing symbiotic interactions in the rhizosphere.     

Food quality of mixed bacteria–algae diets for Daphnia magna

Bacteria can comprise a large fraction of seston in aquatic ecosystems and can therefore significantly contribute to diets of filter-feeding zooplankton. To assess the effect of three heterotrophic bacteria (Flavobacterium sp., Pseudomonas sp. and Escherichia coli) on survival, growth and egg production of juvenile Daphnia magna during six-day growth experiments, five ratios of bacteria–Scenedesmus obliquus mixtures were fed. Potential growth-limiting effects mediated by essential biochemicals were assessed upon supplementation of pure bacterial diets with a sterol (cholesterol) or a polyunsaturated fatty acid (EPA). Pure bacterial diets always had detrimental effects on Daphnia. However, cholesterol supplementation of Flavobacterium sp. enhanced growth rates of Daphnia. Diets containing Pseudomonas impaired Daphnia growth even at low dietary proportions (20%), indicating their toxicity. In contrast, Daphnia grew at relative high dietary proportions of Flavobacterium sp. and E. coli (80–50%). In fact, diets containing small proportions of these heterotrophic bacteria (Flavobacterium ≤50%, E. coli 20%) even significantly increased Daphnia growth rates compared to pure algal diets, indicating a nutritional upgrading by these bacteria. Our results suggest that the relative contribution of bacteria and phytoplankton to total dietary carbon as well as their phylogenetic composition strongly influence Daphnia fitness and potentially other filter-feeding zooplankton under field conditions.     

Endosymbiotic bacteria living inside the poultry red mite (Dermanyssus gallinae)

This study investigated the endosymbiotic bacteria living inside the poultry red mite collected from five samples of one commercial farm from the UK and 16 farms from France using genus-specific PCR, PCR-TTGE and DNA sequencing. Endosymbiotic bacteria are intracellular obligate organisms that can cause several phenotypic and reproductive anomalies to their host and they are found widespread living inside arthropods. The farm sampled from the UK was positive for bacteria of the genera Cardinium sp. and Spiroplasma sp. From France, 7 farms were positive for Cardinium sp., 1 farm was positive for Spiroplasma sp., 1 farm was positive for Rickettsiella sp. and 2 farms were positive for Schineria sp. However, it was not possible to detect the presence of the genus Wolbachia sp. which has been observed in other ectoparasites. This study is the first report of the presence of endosymbionts living inside the poultry red mite. The results obtained suggest that it may be possible that these bacterial endosymbionts cause biological modifications to the poultry red mite.     

Durable and broad-spectrum disease protection measure against airborne phytopathogenic fungi by using the detachment action of gelatinolytic bacteria

We had previously obtained collagenolytic/gelatinolytic bacteria, which degrade the fungal extracellular matrix, to establish a novel biological control measure that inhibits germling adhesion of airborne phytopathogenic fungi on the host plant surface. By using barley-Magnaporthe oryzae pathosystem, Chryseobacterium sp. was most effective biocontrol agents as tested. The selected bacteria were evaluated for durable disease protection against M. oryzae on barley leaves by using chloramphenicol-resistant mutants. Chryseobacterium sp. from the soil was less likely to settle on leaf surfaces. Therefore, we tried to manipulate Chryseobacterium sp. to inhabit the leaf’s surface. The gelatin supplementation dramatically improved the settlement of gelatinolytic bacteria Chryseobacterium sp. from the soil, and the disease protection effect lasted for more than 2 weeks on barley. Moreover, exploitation of Chryseobacterium sp. for disease protection was extended against other airborne pathogens, Alternaria alternata Japanese pear pathotype on Japanese pear and Colletotrichum orbiculare on cucumber.     

Bacterial communities of some brown and red algae from Peter the Great Bay, the Sea of Japan

The structure of microbial communities of brown algae, red algae, and of the red alga Gracilaria verrucosa, healthy and affected with thallus rot, were comparatively investigated; 61 strains of heterotrophic bacteria were isolated and characterized. Most of them were identified to the genus level, some Vibrio spp., to the species level according to their phenotypic properties and the fatty acid composition of cellular lipids. The composition of the microflora of two species of brown algae was different. In Chordaria flagelliphormis, Pseudomonas spp. prevailed, and in Desmarestia viridis, Bacillus spp. The composition of the microflora of two red algae, G. verrucosa and Camphylaephora hyphaeoides, differed mainly in the ratio of prevailing groups of bacteria. The most abundant were bacteria of the CFB cluster and pseudoalteromonads. In addition, the following bacteria were found on the surface of the algae: Sulfitobacter spp., Halomonas spp., Acinetobacter sp., Planococcus sp., Arthrobacter sp., and Agromyces sp. From tissues of the affected G. verrucosa, only vibrios were isolated, both agarolytic and nonagarolytic. The existence of specific bacterial communities characteristic of different species of algae is suggested and the relation of Vibrio sp. to the pathological process in the tissues of G. verrucosa is supposed.     

Staphylococcus sp. KW-07 contains nahH gene encoding catechol 2,3-dioxygenase for phenanthrene degradation and a test in soil microcosm

We isolated three species of phenanthrene-degrading bacteria from oil-contaminated soils and marine sediment, and assessed the potential use of these bacteria for bioremediation of soils contaminated by polycyclic aromatic hydrocarbons (PAHs). Based on 16S rDNA sequences, these bacteria were Staphylococcus sp. KW-07 and Pseudomonas sp. CH-11 from soil, and Ochrobactrum sp. CH-19 from the marine sediment. By PCR amplification, catechol 2,3-dioxygenase genes (nahH genes) mediating PAH degradation in the chromosome of Staphylococcus sp. KW-07 and Ochrobactrum sp. CH-19, and in plasmid DNA of Pseudomonas sp. CH-11 were detected. All isolates had a similar optimal growth temperature (25 °C) and optimal growth pH (7.0) in a minimal salt medium (MSM) with 0.1% (w/v) phenanthrene as the sole source of carbon and energy. Pseudomonas sp. CH-11 and Staphylococcus sp. KW-07 degraded 90% of added phenanthrene in 3 days and Ochrobactrum sp. CH-19 degraded 90% of the phenanthrene in 7 days under laboratory batch culture conditions. However, Staphylococcus sp. KW-07 was the most effective among the three strains in degradation of phenanthrene in soil. After inoculation of 1 × 10¹¹ cells of Staphylococcus sp. KW-07, over 90% degradation of 0.1% phenanthrene (0.1 g/100 g soil) was achieved after 1 month at 25 °C. The results collectively suggest that the Staphylococcus sp. KW-07 strain isolated may be useful in bioremediation of PAH-contaminated soils.     

Construction of cyanobacterial-bacterial consortium on the basis of axenic cyanobacterial cultures and heterotrophic bacteria cultures for bioremediation of oil-contaminated soils and water ponds

The ways of the creation of cyanobacterial-bacterial communities with a high remediation potential for cleaning of oil-contaminated soils and water reservoirs are considered. A special methodology was elaborated for the obtaining of bacteriologically pure (axenic) cultures of cyanobacteria: Phormidium sp. K-1, Oscillatoria sp. A-2, and Oscillatoria sp. C-3. It was shown that 14 strains of bacteria associated with these cyanobacteria manifest a hydrocarbon-oxidizing activity. They belong to the genera Pseudomonas, Alcaligenes, Arthrobacter, and Bacillus. The usage of oil-degrading bacteria, which we isolated from water reservoirs or took from collections, allowed us to construct artificial cyanobacterial-bacterial communities with a high hydrocarbon-oxidizing activity. In field experiments on the landfill site Khimpromservis Aktobe, the high remediatory effect of cyanobacterial-bacterial associations between Phormidium sp. K-1 sp. and bacteria Pseudomonas stutzeri A1, Pseudomonas sp. N2, and P. alcaligenes A5 was demonstrated. The results obtained are the basis for the elaboration of microbiological technologies of environment protection using cyanobacteria.     

Detection of quorum sensing systems of bacteria isolated from fouled marine organisms

N-Acyl homoserine lactones (AHLs or N-AHLs) are a class of signaling molecules involved in bacterial quorum sensing (qs) that have recently been proposed as mediators of the fouling process. In this study, we determined the presence of AHLs in the following marine bacteria strains, which were collected in Santa Marta Bay (Colombia) from heavily fouled surfaces: Ochrobactrum sp., Vibrio sp. (23-6PIN), Vibrio campbellii, Vibrio sp. (11-6DEP), Ochrobactrum pseudogringnonense, Shewanella sp., Vibrio harveyi and Alteromonas sp. The detection and identification of AHLs was conducted using the microbial biosensor Escherichia coli (pSB401) and GC–MS and HPLC-MS analyses. We found that all isolated marine strains had quorum sensing systems mediated by either N-butanoyl homoserine lactone or N-hexanoyl homoserine lactone and in some cases by both. These results are in agreement with the theory that qs is involved in the fouling process. It is noteworthy to mention that we identified qs systems for the first time in bacteria of the genera Ochrobactrum and Alteromonas.     

Arsenic respiration and detoxification by purple non-sulphur bacteria under anaerobic conditions

Two arsenic-resistant purple non-sulphur bacteria (PNSB), Q3B and Q3C, were isolated (from industrial contaminated site and paddy fields) and identified by SSU rRNA gene sequencing as Rhodospirillum and Rhodospirillaceae species, respectively. Maximum arsenic reduction by these PNSB was observed in anaerobic conditions. Rhodospirillum sp. Q3B showed 74.92% (v/v) arsenic reduction while Rhodospirillaceae sp. Q3C reduced arsenic up to 76.67% (v/v) in anaerobic conditions. Rhodospirillaceae sp. Q3C was found to contain highest carotenoid content up to 5.6 mg·g⁻¹. Under anaerobic conditions, the isolates were able to respire arsenic in the presence of lactate, citrate, and oxalate. Rhodospirillum sp. Q3B and Rhodospirillaceae sp. Q3C were also found to produce hydrogen gas. Such diverse bacteria can be useful tools for bioremediation purposes. These bacteria can be further exploited and optimized to treat wastewater containing arsenic along with bio-hydrogen production.     

A prevalent alpha-proteobacterium Paracoccus sp. in a population of the Cayenne ticks (Amblyomma cajennense) from Rio de Janeiro,Brazil

As Rocky Mountain Spotted Fever is the most common tick-borne disease in South America, the presence of Rickettsia sp. in Amblyomma ticks is a possible indication of its endemicity in certain geographic regions. In the present work, bacterial DNA sequences related to Rickettsia amblyommii genes in A. dubitatum ticks, collected in the Brazilian state of Mato Grosso, were discovered. Simultaneously, Paracoccus sp. was detected in aproximately 77% of A. cajennense specimens collected in Rio de Janeiro, Brazil. This is the first report of Paracoccus sp. infection in a specific tick population, and raises the possibility of these bacteria being maintained and/or transmitted by ticks. Whether Paracoccus sp. represents another group of pathogenic Rhodobacteraceae or simply plays a role in A. cajennense physiology, is unknown. The data also demonstrate that the rickettsial 16S rRNA specific primers used forRickettsia spp. screening can also detect Paracoccus alpha-proteobacteria infection in biological samples. Hence, a PCR-RFLP strategy is presented to distinguish between these two groups of bacteria.