Microdiverse bacterial clades prevail across Antarctic wetlands.

Antarctica's extreme environmental conditions impose selection pressures on microbial communities. Indeed, a previous study revealed that bacterial assemblages at the Cierva Point Wetland Complex (CPWC) are shaped by strong homogeneous selection. Yet which bacterial phylogenetic clades are shaped by selection processes and their ecological strategies to thrive in such extreme conditions remain unknown. Here, we applied the phyloscore and feature-level ßNTI indexes coupled with phylofactorization to successfully detect bacterial monophyletic clades subjected to homogeneous (HoS) and heterogenous (HeS) selection. Remarkably, only the HoS clades showed high relative abundance across all samples and signs of putative microdiversity. The majority of the amplicon sequence variants (ASVs) within each HoS clade clustered into a unique 97% sequence similarity operational taxonomic unit (OTU) and inhabited a specific environment (lotic, lentic or terrestrial). Our findings suggest the existence of microdiversification leading to sub-taxa niche differentiation, with putative distinct ecotypes (consisting of groups of ASVs) adapted to a specific environment. We hypothesize that HoS clades thriving in the CPWC have phylogenetically conserved traits that accelerate their rate of evolution, enabling them to adapt to strong spatio-temporally variable selection pressures. Variable selection appears to operate within clades to cause very rapid microdiversification without losing key traits that lead to high abundance. Variable and homogeneous selection, therefore, operate simultaneously but on different aspects of organismal ecology. The result is an overall signal of homogeneous selection due to rapid within-clade microdiversification caused by variable selection. It is unknown whether other systems experience this dynamic, and we encourage future work evaluating the transferability of our results.

Biodegradation of chloroethene compounds under microoxic conditions.

The biodegradation of chloroethene compounds under oxic and anoxic conditions is well established. However, the biological reactions that take place under microoxic conditions are unknown. Here, we report the biostimulated (BIOST: addition of lactate) and natural attenuated (NAT) degradation of chloroethene compounds under microoxic conditions by bacterial communities from chloroethene compounds-contaminated groundwater. The degradation of tetrachloroethene was significantly higher in NAT (15.14% on average) than in BIOST (10.13% on average) conditions at the end of the experiment (90 days). Sporomusa, Paracoccus, Sedimentibacter, Pseudomonas, and Desulfosporosinus were overrepresented in NAT and BIOST compared to the source groundwater. The NAT metagenome contains phenol hydrolase P1 oxygenase (dmpL), catechol-1,2-dioxygenase (catA), catechol-2,3-dioxygenases (dmpB, todE, and xylE) genes, which could be involved in the cometabolic degradation of chloroethene compounds; and chlorate reductase (clrA), that could be associated with partial reductive dechlorination of chloroethene compounds. Our data provide a better understanding of the bacterial communities, genes, and pathways potentially implicated in the reductive and cometabolic degradation of chloroethene compounds under microoxic conditions.

A metagenomic survey of the fecal microbiome of the African savanna elephant (Loxodonta africana).

The African savanna elephant (Loxodonta africana) is the largest terrestrial animal on Earth and is found primarily in Southern and Eastern Africa. It is a hindgut, colonic fermenter and subsists on a diet of raw plant materials found in its grazing area. In this study the bacterial, archaeal and fungal populations of seven African savanna elephant fecal metagenomes were first characterized using amplicon sequencing. On the genus level it was observed that the p-1088-a5 gut group in the bacteriome, Methanocorpusulum and Methanobrevibacter in the archaeome and Alternaria, Aurobasidium, Didymella and Preussia in the mycome, predominated. Subsequently, metagenomic shotgun sequencing was employed to identify possible functional pathways and carbohydrate-active enzymes (CAZymes). Carbohydrate catabolic pathways represented the main degradation pathways, and the fecal metagenome was enriched in the glycohydroside (GH) class of CAZymes. Additionally, the top GH families identified - GH43, GH2, GH13 and GH3 - are known to be associated with cellulytic, hemicellulytic and pectolytic activities. Finally, the CAZymes families identified in the African savanna elephant were compared with those found in the Asian elephant and it was demonstrated that there is a unique repository of CAZymes that could be leveraged in the biotechnological context such as the degradation of lignocellulose for the production of second-generation biofuels and energy.

Characterization of the soil resistome and mobilome in Namib Desert soils.

The study of the soil resistome is important in understanding the evolution of antibiotic resistance and its dissemination between the clinic and the environment. However, very little is known about the soil resistome, especially of those from deserts. Here, we characterize the bacterial communities, using targeted sequencing of the 16S rRNA genes, and both the resistome and the mobilome in Namib Desert soils, using shotgun metagenomics. We detected a variety of antibiotic resistance genes (ARGs) that conferred resistance to antibiotics such as elfamycin, rifampicin, and fluoroquinolones, metal/biocide resistance genes (MRGs/BRGs) conferring resistance to metals such as arsenic and copper, and mobile genetic elements (MGEs) such as the ColE1-like plasmid. The presence of metal/biocide resistance genes in close proximity to ARGs indicated a potential for co-selection of resistance to antibiotics and metals/biocides. The co-existence of MGEs and horizontally acquired ARGs most likely contributed to a decoupling between bacterial community composition and ARG profiles. Overall, this study indicates that soil bacterial communities in Namib Desert soils host a diversity of resistance elements and that horizontal gene transfer, rather than host phylogeny, plays an essential role in their dynamics.

The ecological assembly of bacterial communities in Antarctic wetlands varies across levels of phylogenetic resolution.

As functional traits are conserved at different phylogenetic depths, the ability to detect community assembly processes can be conditional on the phylogenetic resolution; yet most previous work quantifying their influence has focused on a single level of phylogenetic resolution. Here, we have studied the ecological assembly of bacterial communities from an Antarctic wetland complex, applying null models across different levels of phylogenetic resolution (i.e. clustering ASVs into OTUs with decreasing sequence identity thresholds). We found that the relative influence of the community assembly processes varies with phylogenetic resolution. More specifically, selection processes seem to impose stronger influence at finer (100% sequence similarity ASV) than at coarser (99%-97% sequence similarity OTUs) resolution. We identified environmental features related with the ecological processes and propose a conceptual model for the bacterial community assembly in this Antarctic ecosystem. Briefly, eco-evolutionary processes appear to be leading to different but very closely related ASVs in lotic, lentic and terrestrial environments. In all, this study shows that assessing community assembly processes at different phylogenetic resolutions is key to improve our understanding of microbial ecology. More importantly, a failure to detect selection processes at coarser phylogenetic resolution does not imply the absence of such processes at finer resolutions.

Differences in Precipitation Regime Shape Microbial Community Composition and Functional Potential in Namib Desert Soils.

Precipitation is one of the major constraints influencing the diversity, structure, and activity of soil microbial communities in desert ecosystems. However, the effect of changes in precipitation on soil microbial communities in arid soil microbiomes remains unresolved. In this study, using 16S rRNA gene high-throughput sequencing and shotgun metagenome sequencing, we explored changes in taxonomic composition and functional potential across two zones in the Namib Desert with contrasting precipitation regime. We found that precipitation regime had no effect on taxonomic and functional alpha-diversity, but that microbial community composition and functional potential (beta-diversity) changed with increased precipitation. For instance, Acidobacteriota and 'resistance to antibiotics and toxic compounds' related genes were relatively more abundant in the high-rainfall zone. These changes were largely due to a small set of microbial taxa, some of which were present in low abundance (i.e. members of the rare biosphere). Overall, these results indicate that key climatic factors (i.e. precipitation) shape the taxonomic and functional attributes of the arid soil microbiome. This research provides insight into how changes in precipitation patterns associated with global climate change may impact microbial community structure and function in desert soils.

Novel lichen-dominated hypolithic communities in the Namib Desert.

The ventral surfaces of translucent rocks from hot desert pavements often harbor hypolithic microbial communities, which are mostly dominated by cyanobacteria. The Namib Desert fog belt supports extensive hypolithic colonization of quartz rocks, which are also colonized by lichens on their dorsal surfaces. Here, we aim to evaluate whether lichens colonize the ventral surface of the rocks (i.e., show hypolithic lifestyle) and compare the bacterial composition of these coastal hypolithic communities with those found inland. Fungal DNA barcoding and fungal and bacterial Illumina metabarcoding were combined with electron microscopy to characterize the composition and spatial structure of hypolithic communities from two (coastal and inland) areas in the Namib Desert. We report, for the first time, the structure and composition of lichen-dominated hypolithic communities found in the coastal zone of the Namib Desert with extensive epilithic lichen cover. Lichen modified areoles with inverted morphology of the genus Stellarangia (three lineages) and Buellia (two lineages) were the main components of these hypolithic communities. Some of these lineages were also found in epilithic habitats. These lichen-dominated hypolithic communities differed in structural organization and bacterial community composition from those found in inland areas. The hypolithic lichen colonization characterized here seems not to be an extension of epilithic or biological soil crust lichen growths but the result of specific sublithic microenvironmental conditions. Moisture derived from fog and dew could be the main driver of this unique colonization.

Pollution shapes the microbial communities in river water and sediments from the Olifants River catchment, South Africa.

Human activities such as agriculture and mining are leading causes of water pollution worldwide. Individual contaminants are known to negatively affect microbial communities. However, the effect of multifaceted pollution on these communities is less well understood. We investigated, using next-generation sequencing of the 16S rRNA genes, the effects of multisource (i.e., fertilizer industry and mining) chronic pollution on bacterial and archaeal communities in water and sediments from the Olifants River catchment, South Africa. Water samples showed less microbial species diversity than sediments and both habitats displayed different microbial communities. Within each of these habitats, pollution had no effect on alpha diversity but shaped the microbial composition and taxonomy-based predicted functions. Certain prokaryotic taxa and functional groups were indicative of different degrees of pollution. Heterotrophic taxa (e.g., Flavobacterium sp.) and sulphur-oxidizing bacteria (i.e., Thiobacillus sp.) were indicators of pollution in water and sediments, respectively. Ultimately, this information could be used to develop microbial indicators of water quality degradation.

The Functional Potential of the Rhizospheric Microbiome of an Invasive Tree Species, Acacia dealbata.

Plant-microbe interactions mediate both the invasiveness of introduced plant species and the impacts that they have in invaded ecosystems. Although the phylogenetic composition of the rhizospheric microbiome of Acacia dealbata (an invasive Australian tree species) has been investigated, little is known about the functional potential of the constituents of these altered microbial communities. We used shotgun DNA sequencing to better understand the link between bacterial community composition and functional capacity in the rhizospheric microbiomes associated with invasive A. dealbata populations in South Africa. Our analysis showed that several genes associated with plant growth-promoting (PGP) traits were significantly overrepresented in the rhizospheric metagenomes compared to neighbouring bulk soils collected away from A. dealbata stands. The majority of these genes are involved in the metabolism of nitrogen, carbohydrates and vitamins, and in various membrane transport systems. Overrepresented genes were linked to a limited number of bacterial taxa, mostly Bradyrhizobium species, the preferred N-fixing rhizobial symbiont of Australian acacias. Overall, these findings suggest that A. dealbata enriches rhizosphere soils with potentially beneficial microbial taxa, and that members of the genus Bradyrhizobium may play an integral role in mediating PGP processes that may influence the success of this invader when colonizing novel environments.

Aerobic and anaerobic enrichment cultures highlight the pivotal role of facultative anaerobes in soil hydrocarbon degradation.

Aliphatic and aromatic hydrocarbons are ubiquitous in the environment due to natural and anthropogenic processes. Under aerobic conditions hydrocarbons can be rapidly biodegraded but oxygenated environments often quickly become anaerobic when microbial respiration is coupled to contaminant oxidation. Most studies in literature usually focus on the initial microbial diversity of the hydrocarbon impacted environment and examine either aerobic or anaerobic conditions for enrichment. Hence, the aim of the present study was to enrich bacterial consortiums from two diesel impacted soil samples under both these conditions to assess the enrichment diversities and hydrocarbon degradation potentials. This would shed light upon how an environmental population shift would correlate to oxygen intrusion and depletion and still continue hydrocarbon degradation. Analysis of the 16S rRNA gene sequences showcases the different microbial populations that could emerge as the environmental factors change, resulting in different populations that are still capable of hydrocarbon degradation. Microbial diversity analysis also highlights the role of facultative anaerobic bacteria like Pseudomonas spp. and Citrobacter spp. in maintaining hydrocarbon degradation. This study shows that microorganisms capable of surviving under both oxic and anoxic (aerobic and anaerobic) conditions are the most crucial to the long term degradation of hydrocarbons in the environment.

Cyanobacteria drive community composition and functionality in rock-soil interface communities.

Most ecological research on hypoliths, significant primary producers in hyperarid deserts, has focused on the diversity of individual groups of microbes (i.e. bacteria). However, microbial communities are inherently complex, and the interactions between cyanobacteria, heterotrophic bacteria, protista and metazoa are likely to be very important for ecosystem functioning. Cyanobacterial and heterotrophic bacterial communities were analysed by pyrosequencing, while metazoan and protistan communities were assessed by T-RFLP analysis. Microbial functionality was estimated using carbon substrate utilization. Cyanobacterial community composition was significant in shaping community structure and function in hypoliths. Ecological network analysis showed that most significant co-occurrences were positive, representing potential synergistic interactions. There were several highly interconnected associations (modules), and specific cyanobacteria were important in driving the modular structure of hypolithic networks. Together, our results suggest that hypolithic cyanobacteria have strong effects on higher trophic levels and ecosystem functioning.

Pseudomonas punonensis sp. nov., isolated from straw.

During a study of the 'tunta' (frozen-dry potato) production process in Peru, a bacterial strain, LMT03(T), was isolated from the straw grass in which the potatoes are dried. This strain was classified into the genus Pseudomonas on the basis of the 16S rRNA gene sequence analysis, and is most closely related to Pseudomonas argentinensis CH01(T) with 99.3 % identity in this gene and 96 %, 92 % and 86 % identities in rpoB, rpoD and gyrB genes, respectively. Strain LMT03(T) has a single polar flagellum, like other related yellow-pigment-producing pseudomonads. The major quinone is Q-9. The major fatty acids are C18 : 1ω7c in summed feature 8 (40.82 %), C16 : 1ω6c/C16 : 1ω6c in summed feature 3 (23.72 %) and C16 : 0 (15.20 %). The strain produces oxidase but it does not produce gelatinase, indole, urease, arginine dihydrolase or ß-galactosidase. Catalase production was very weak after 28 and 48 h incubation on nutrient agar medium. Nitrate reduction is negative. It does not hydrolyse aesculin. The DNA G+C content is 57.8 mol%. DNA-DNA hybridization results showed lower than 52 % relatedness with respect to the type strain of P. argentinensis, CH01(T). These results, together with other phenotypic characteristics, support the definition of a novel species within the genus Pseudomonas, for which the name Pseudomonas punonensis sp. nov. is proposed. The type strain is LMT03(T) ( = LMG 26839(T) = CECT 8089(T)).

Phyllobacterium endophyticum sp. nov., isolated from nodules of Phaseolus vulgaris.

A strain, PEPV15(T), was isolated from a nodule on Phaseolus vulgaris grown in soil in northern Spain. Phylogenetic analyses of 16S rRNA and atpD genes showed that this strain belongs to the genus Phyllobacterium. The most closely related species were, in both cases, Phyllobacterium brassicacearum, Phyllobacterium bourgognense and Phyllobacterium trifolii, the type strains of which gave sequence similarities of 98.9, 98.6 and 98.4 %, respectively, in the 16S rRNA gene and 88.1, 87.5 and 88.7 %, respectively, in the atpD gene. PEPV15(T) contained Q-10 as the major quinone (88 %) and low amounts of Q-9 (12 %). It differed from its closest relatives in its growth in diverse culture conditions and in the assimilation of several carbon sources. The strain was not able to produce nodules in Phaseolus vulgaris. The results of DNA-DNA hybridization, phenotypic tests and fatty acid analyses confirmed that this strain represents a novel species of the genus Phyllobacterium for which the name Phyllobacterium endophyticum sp. nov. is proposed; the type strain is PEPV15(T) ( = LMG 26470(T) = CECT 7949(T)). An emended description of the genus Phyllobacterium is also provided.

Hypolithic and soil microbial community assembly along an aridity gradient in the Namib Desert.

The Namib Desert is considered the oldest desert in the world and hyperarid for the last 5 million years. However, the environmental buffering provided by quartz and other translucent rocks supports extensive hypolithic microbial communities. In this study, open soil and hypolithic microbial communities have been investigated along an East-West transect characterized by an inverse fog-rainfall gradient. Multivariate analysis showed that structurally different microbial communities occur in soil and in hypolithic zones. Using variation partitioning, we found that hypolithic communities exhibited a fog-related distribution as indicated by the significant East-West clustering. Sodium content was also an important environmental factor affecting the composition of both soil and hypolithic microbial communities. Finally, although null models for patterns in microbial communities were not supported by experimental data, the amount of unexplained variation (68-97 %) suggests that stochastic processes also play a role in the assembly of such communities in the Namib Desert.

Legume Overseeding and P Fertilization Increases Microbial Activity and Decreases the Relative Abundance of AM Fungi in Pampas Natural Pastures.

Natural grasslands provide a valuable resource for livestock grazing. In many parts of South America, legume overseeding and P fertilization are commonly used to enhance primary productivity. The effect of this practice on the plant community is well established. However, how this management regime affects the soil microbiome is less known. Here, to contribute to filling this knowledge gap, we analyzed the effect of Lotus subbiflorus overseeding, together with P fertilization, on soil microbial community diversity and activity in the Uruguayan Pampa region. The results showed that plant communities in the natural grassland paddocks significantly differed from those of the managed paddocks. In contrast, neither microbial biomass and respiration nor microbial diversity was significantly affected by management, although the structure of the bacterial and fungal communities were correlated with those of the plant communities. AM Fungi relative abundance, as well as several enzyme activities, were significantly affected by management. This could have consequences for the C, N, and P content of SOM in these soils, which in turn might affect SOM degradation.

Herbaspirillum canariense sp. nov., Herbaspirillum aurantiacum sp. nov. and Herbaspirillum soli sp. nov., isolated from volcanic mountain soil, and emended description of the genus Herbaspirillum.

Three Gram-negative, motile and slightly curved rod-shaped bacteria, strains SUEMI03(T), SUEMI08(T) and SUEMI10(T), were isolated from an old volcanic mountain soil on Tenerife (Canary Islands). The three strains were related phylogenetically to Herbaspirillum seropedicae. 16S rRNA gene sequence similarity was 99.2-99.6 % among strains SUEMI03(T), SUEMI08(T) and SUEMI10(T), which presented 97.5, 97.8 and 97.7 % identity, respectively, with respect to H. seropedicae DSM 6445(T). The three strains grew optimally in TSB at 28 °C and contained summed features 3 (C(16:1)ω6c and/or C(16:1)ω7c) and 8 (C(18:1)ω6c and/or C(18:1)ω7c) and C(16:0) as major cellular fatty acids. The DNA G+C contents of strains SUEMI03(T), SUEMI08(T) and SUEMI10(T) were 61.6, 60.4 and 61.9 mol%, respectively. Strains SUEMI03(T), SUEMI08(T) and SUEMI10(T) presented less than 60 % interstrain DNA relatedness and less than 30 % relatedness with respect to H. seropedicae DSM 6445(T). In spite of their common geographical origin, the three strains isolated in this study presented several phenotypic differences, presenting phenotypic profiles highly divergent from that of H. seropedicae. Therefore, we propose that the strains isolated in this study represent three novel species of the genus Herbaspirillum, named Herbaspirillum canariense sp. nov. (type strain SUEMI03(T) = LMG 26151(T) = CECT 7838(T)), Herbaspirillum aurantiacum sp. nov. (type strain SUEMI08(T) = LMG 26150(T) = CECT 7839(T)) and Herbaspirillum soli sp. nov. (type strain SUEMI10(T) = LMG 26149(T) = CECT 7840(T)).

Biogeography of bacterial communities in hot springs: a focus on the actinobacteria.

Actinobacteria are ubiquitous in soil, freshwater and marine ecosystems. Although various studies have focused on the microbial ecology of this phylum, data are scant on the ecology of actinobacteria endemic to hot springs. Here, we have investigated the molecular diversity of eubacteria, with specific focus on the actinobacteria in hot springs in Zambia, China, New Zealand and Kenya. Temperature and pH values at sampling sites ranged between 44.5 and 86.5 °C and 5-10, respectively. Non-metric multidimensional scaling analysis of 16S rRNA gene T-RFLP patterns showed that samples could be separated by geographical location. Multivariate analysis showed that actinobacterial community composition was best predicted by changes in pH and temperature, whereas temperature alone was the most important variable explaining differences in bacterial community structure. Using 16S rRNA gene libraries, 28 major actinobacterial OTUs were found. Both molecular techniques indicated that many of the actinobacterial phylotypes were unique and exclusive to the respective sample. Collectively, these results support the view that both actinobacterial diversity and endemism are high in hot spring ecosystems.

Evidence of an American origin for symbiosis-related genes in Rhizobium lusitanum.

Randomly amplified polymorphic DNA (RAPD) analysis was used to investigate the diversity of 179 bean isolates recovered from six field sites in the Arcos de Valdevez region of northwestern Portugal. The isolates were divided into 6 groups based on the fingerprint patterns that were obtained. Representatives for each group were selected for sequence analysis of 4 chromosomal DNA regions. Five of the groups were placed within Rhizobium lusitanum, and the other group was placed within R. tropici type IIA. Therefore, the collection of Portuguese bean isolates was shown to include the two species R. lusitanum and R. tropici. In plant tests, the strains P1-7, P1-1, P1-2, and P1-16 of R. lusitanum nodulated and formed nitrogen-fixing symbioses both with Phaseolus vulgaris and Leucaena leucocephala. A methyltransferase-encoding nodS gene identical with the R. tropici locus that confers wide host range was detected in the strain P1-7 as well as 24 others identified as R. lusitanum. A methyltransferase-encoding nodS gene also was detected in the remaining isolates of R. lusitanum, but in this case the locus was that identified with the narrow-host-range R. etli. Representatives of isolates with the nodS of R. etli formed effective nitrogen-fixing symbioses with P. vulgaris and did not nodulate L. leucocephala. From sequence data of nodS, the R. lusitanum genes for symbiosis were placed within those of either R. tropici or R. etli. These results would support the suggestion that R. lusitanum was the recipient of the genes for symbiosis with beans from both R. tropici and R. etli.

Lactococcus lactis subsp. tructae subsp. nov. isolated from the intestinal mucus of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss).

The species Lactococcus lactis currently includes three subspecies; L. lactis subsp. lactis and L. lactis subsp. cremoris, isolated from milk sources, and L. lactis subsp. hordniae, isolated from the leafhopper Hordnia circellata. In this study, three strains, designated L105(T), I3 and L101, were isolated from the intestinal mucus of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss). These strains were closely related to members of the species Lactococcus lactis. Strain L105(T) showed 99.4 % 16S rRNA gene sequence similarity to that of the type strains L. lactis subsp. lactis NCDO 604(T) and L. lactis subsp. hordniae NCDO 2181(T) and showed 99.9 % similarity to the type strain Lactococcus lactis subsp. cremoris NCDO 607(T). Analysis of two housekeeping genes, rpoB and recA, confirmed the close relationship between the novel strains and L. lactis subsp. cremoris with similarities of 99.3 and 99.7 %, respectively. The three strains could, however, be differentiated from their closest relatives on the basis of several phenotypic characteristics, as was the case for L. lactis subsp. lactis and L. lactis subsp. hordniae, which were also closely related on the basis of 16S rRNA, rpoB and recA gene sequence similarities. The strains isolated in this study represent a new subspecies, for which the name Lactococcus lactis subsp. tructae subsp. nov. is proposed. The type strain is L105(T) ( = LMG 24662(T)  = DSM 21502(T)).

Strains nodulating Lupinus albus on different continents belong to several new chromosomal and symbiotic lineages within Bradyrhizobium.

In this work we analysed different chromosomal and symbiotic markers in rhizobial strains nodulating Lupinus albus (white lupin) in several continents. Collectively the analysis of their rrs and atpD genes, and 16S-23S intergenic spacers (ITS), showed that they belong to at least four chromosomal lineages within the genus Bradyrhizobium. Most isolates from the Canary Islands (near to the African continent) grouped with some strains isolated on mainland Spain and were identified as Bradyrhizobium canariense. These strains are divided into two ITS subgroups coincident with those previously described from isolates nodulating Ornithopus. The remaining strains isolated on mainland Spain grouped with most isolates from Chile (American continent) forming a new lineage related to Bradyrhizobium japonicum. The strains BLUT2 and ISLU207 isolated from the Canary Islands and Chile, respectively, formed two new lineages phylogenetically close to different species of Bradyrhizobium depending on the marker analyzed. The analysis of the nodC gene showed that all strains nodulating L. albus belong to the biovar genistearum; nevertheless they form four different nodC lineages of which lineage C is at present exclusively formed by L. albus endosymbionts isolated from different continents.