Whole genome analysis of the
genus using average nucleotide identity (ANI) and phylogenomics showed the genus to be essentially monophyletic with seven robust groups within this taxon that includes ...nitrogen-fixing nodule forming bacteria as well as free living strains. Despite the wide genetic diversity of these bacteria no indication was found to suggest that the
genus have to split in different taxa. Bradyrhizobia have larger genomes than other genera of the Bradyrhizobiaceae family, probably reflecting their metabolic diversity and different lifestyles. Few plasmids in the sequenced strains were revealed from
gene analysis and a relatively low proportion of the genome is devoted to mobile genetic elements. Sequence diversity of
and
gene metadata was used to theoretically estimate the number of existing species and to predict how many would exist. There may be many more species than those presently described with predictions of around 800 species in nature. Different arguments are presented suggesting that nodulation might have arose in the ancestral genus
.
Many studies on the microbiome of animals have been reported but a comprehensive analysis is lacking. Here we present a meta-analysis on the microbiomes of arthropods and their terrestrial habitat, ...focusing on the functional profile of bacterial communities derived from metabolic traits that are essential for microbial life. We report a detailed analysis of probably the largest set of biochemically defined functional traits ever examined in microbiome studies. This work deals with the phylum proteobacteria, which is usually dominant in marine and terrestrial environments and covers all functions associated with microbiomes. The considerable variation in the distribution and abundance of proteobacteria in microbiomes has remained fundamentally unexplained. This analysis reveals discrete functional groups characteristic for adaptation to anaerobic conditions, which appear to be defined by environmental filtering of taxonomically related taxa. The biochemical diversification of the functional groups suggests an evolutionary trajectory in the structure of arthropods' microbiome, from metabolically versatile to specialized proteobacterial organisms that are adapted to complex environments such as the gut of social insects. Bacterial distribution in arthropods' microbiomes also shows taxonomic clusters that do not correspond to functional groups and may derive from other factors, including common contaminants of soil and reagents.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Nitrogen Fixation in Cereals Rosenblueth, Mónica; Ormeño-Orrillo, Ernesto; López-López, Aline ...
Frontiers in microbiology,
08/2018, Letnik:
9
Journal Article
Recenzirano
Odprti dostop
Cereals such as maize, rice, wheat and sorghum are the most important crops for human nutrition. Like other plants, cereals associate with diverse bacteria (including nitrogen-fixing bacteria called ...diazotrophs) and fungi. As large amounts of chemical fertilizers are used in cereals, it has always been desirable to promote biological nitrogen fixation in such crops. The quest for nitrogen fixation in cereals started long ago with the isolation of nitrogen-fixing bacteria from different plants. The sources of diazotrophs in cereals may be seeds, soils, and even irrigation water and diazotrophs have been found on roots or as endophytes. Recently, culture-independent molecular approaches have revealed that some rhizobia are found in cereal plants and that bacterial nitrogenase genes are expressed in plants. Since the levels of nitrogen-fixation attained with nitrogen-fixing bacteria in cereals are not high enough to support the plant's needs and never as good as those obtained with chemical fertilizers or with rhizobium in symbiosis with legumes, it has been the aim of different studies to increase nitrogen-fixation in cereals. In many cases, these efforts have not been successful. However, new diazotroph mutants with enhanced capabilities to excrete ammonium are being successfully used to promote plant growth as commensal bacteria. In addition, there are ambitious projects supported by different funding agencies that are trying to genetically modify maize and other cereals to enhance diazotroph colonization or to fix nitrogen or to form nodules with nitrogen-fixing symbiotic rhizobia.
Recent molecular studies on endophytic bacterial diversity have revealed a large richness of species. Endophytes promote plant growth and yield, suppress pathogens, may help to remove contaminants, ...solubilize phosphate, or contribute assimilable nitrogen to plants. Some endophytes are seed-borne, but others have mechanisms to colonize the plants that are being studied. Bacterial mutants unable to produce secreted proteins are impaired in the colonization process. Plant genes expressed in the presence of endophytes provide clues as to the effects of endophytes in plants. Molecular analysis showed that plant defense responses limit bacterial populations inside plants. Some human pathogens, such as Salmonella spp., have been found as endophytes, and these bacteria are not removed by disinfection procedures that eliminate superficially occurring bacteria. Delivery of endophytes to the environment or agricultural fields should be carefully evaluated to avoid introducing pathogens.
The legume genus Mimosa has > 500 species, with two major centres of diversity, Brazil (c. 350 spp.) and Mexico (c. 100 spp.). In Brazil most species are nodulated by Burkholderia. Here we asked ...whether this is also true of native and endemic Mexican species.
We have tested this apparent affinity for betaproteobacteria by examining the symbionts of native and endemic species of Mimosa in Mexico, especially from the central highlands where Mimosa spp. have diversified. Nodules were tested for betaproteobacteria using in situ immunolocalization. Rhizobia isolated from the nodules were genetically characterized and tested for their ability to nodulate Mimosa spp.
Immunological analysis of 25 host taxa suggested that most (including all the highland endemics) were not nodulated by betaproteobacteria. Phylogenetic analyses of 16S rRNA, recA, nodA, nodC and nifH genes from 87 strains isolated from 20 taxa confirmed that the endemic Mexican Mimosa species favoured alphaproteobacteria in the genera Rhizobium and Ensifer: this was confirmed by nodulation tests.
Host phylogeny, geographic isolation and coevolution with symbionts derived from very different soils have potentially contributed to the striking difference in the choice of symbiotic partners by Mexican and Brazilian Mimosa species.
Herein the members of the Subcommittee on Taxonomy of Rhizobia and Agrobacteria of the International Committee on Systematics of Prokaryotes review recent developments in rhizobial and agrobacterial ...taxonomy and propose updated minimal standards for the description of new species (and genera) in these groups. The essential requirements (minimal standards) for description of a new species are (1) a genome sequence of at least the proposed type strain and (2) evidence for differentiation from other species based on genome sequence comparisons. It is also recommended that (3) genetic variation within the species is documented with sequence data from several clearly different strains and (4) phenotypic features are described, and their variation documented with data from a relevant set of representative strains. Furthermore, it is encouraged that information is provided on (5) nodulation or pathogenicity phenotypes, as appropriate, with relevant gene sequences. These guidelines supplement the current rules of general bacterial taxonomy, which require (6) a name that conforms to the International Code of Nomenclature of Prokaryotes, (7) validation of the name by publication either directly in the International Journal of Systematic and Evolutionary Microbiology or in a validation list when published elsewhere, and (8) deposition of the type strain in two international culture collections in separate countries.
Clinicians' risk behaviors, including their personal alcohol use, may influence patients' attitudes and motivation to make changes in their lifestyle, as well as the provision of clinical preventive ...services to reduce unhealthy behaviors. The aim of the systematic review was to summarize the existing evidence on the association between clinicians' alcohol consumption and their preventive practices to reduce unhealthy alcohol use. The review was conducted following Cochrane guidelines and Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) statement guidance. Three databases (Cochrane, MEDLINE, Web of Science) were queried from July 1, 2021, through November 30, 2021. We included quantitative observational studies reporting clinicians' alcohol use associations with relevant preventive practices. Two reviewers independently screened articles for inclusion, extracted data, and assessed the quality of selected studies. Ten studies, published from 1986 to 2018, were included. We found a statistically significant association between clinicians' alcohol consumption and their preventive practices to reduce unhealthy alcohol use in eight of the 10 studies. Clinicians who drank larger quantities of alcohol offered less screening and counseling to their patients about alcohol use. Clinicians who drank regularly (3 days a week or more) were less likely to screen for alcohol use, and the frequency of alcohol use by those professionals was inversely related to recommending quitting. Clinicians' alcohol use appears to be associated with their screening for unhealthy alcohol use and counseling to reduce it. The frequency and quantity of clinicians' alcohol consumption were also associated with their practices to address unhealthy alcohol use.
Legume specificity is encoded in rhizobial genetic elements that may be transferred among species and genera. Dissemination (by lateral transfer) of gene assemblies dictating host range accounts for ...the existence of the same biological variant (biovar) in distinct microbiological species. Different alternative biovars may exist in a single species expanding their adaptation to different niches (legume nodules). A review of all reported biovars is presented. Instead of the term biovar, symbiotic variant (symbiovar) is proposed as a parallel term to pathovar in pathogenic bacteria. Symbiovars should be determined based on the symbiotic capabilities in plant hosts, distinguished by the differences in host range and supported by symbiotic gene sequence information.
Folates in legume root nodules Banuelos, Jacob; Martínez‐Romero, Esperanza; Montaño, Noé Manuel ...
Physiologia plantarum,
March 2021, 2021-Mar, 2021-03-00, 20210301, Letnik:
171, Številka:
3
Journal Article
Recenzirano
Folates are multifunctional metabolites in plants that are essential for cell division, nucleic acids and amino acid synthesis. During symbiotic nitrogen fixation in legumes, these cofactors are ...needed for de novo purine biosynthesis, meaning that changes in the folate pools could directly affect the flow of fixed nitrogen to the plant. Its role related to symbiotic nitrogen fixation has not been yet explored, but recent data suggest a relevant role during the first steps. Transcriptomic, metabolomic and proteomic analyses indicate that folates are accumulated in symbiotic plant tissue, as they are involved, not only in de novo purines biosynthesis, but in nitrogen translocation, endoreduplication and phytohormones biosynthesis. Understanding the possible implication of folate pools during the nitrogen fixation and assimilation, might aid for new engineering targets, in relation to the two transformylations or the production of glycine by serine hydroxymethyltransferase during the de novo purine biosynthetic pathway. In this review, we intend to deliver and discuss the available evidence that support a relevant role of folates during the symbiotic nitrogen fixation.
Bradyrhizobium japonicum was described from soybean root-nodule bacterial isolates. Since its description, several studies have revealed heterogeneities among rhizobia assigned to this species. ...Strains assigned to B. japonicum group Ia have been isolated in several countries, and many of them are outstanding soybean symbionts used in inoculants worldwide, but they have also been isolated from other legume hosts. Here, we summarize published studies that indicate that group Ia strains are different from the B. japonicum type strain USDA 6T and closely related strains, and present new morphophysiological, genotypic and genomic evidence to support their reclassification into a novel species, for which the name Bradyrhizobium diazoefficiens sp. nov. is proposed. The type strain of the novel species is the well-studied strain USDA 110T ( = IAM 13628T = CCRC 13528T = NRRL B-4361T = NRRL B-4450T = TAL 102T = BCRC 13528T = JCM 10833T = TISTR 339T = SEMIA 5032T = 3I1B110T = ACCC 15034T = CCT 4249T = NBRC 14792T = R-12974T = CNPSo 46T).
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