Search

Lagoon systems are often confined, and their waters are poorly renewed, which makes them vulnerable to pollutants’ accumulation. Here, the impact of different sources of anthropogenic contamination (domestic, urban, industrial, and agricultural) on the nitrate (NO) content, emission of the greenhouse gas nitrous oxide (NO), abundance of total bacterial archaeal, nitrifying, and denitrifying communities, and diversity and composition of bacterial communities in the sediments of the RAMSAR-protected Marchica lagoon (Nador, Morocco) was investigated. Six lake sites differing in NO concentration were selected. Wastewater coming from industrial activities results in the greatest concentration of NO in sediments and emissions of NO. Increased carbon to nitrogen content in sites near domestic activities resulted in an increase in the abundance of total bacterial and archaeal communities, as well as nitrification and denitrification genes, but low NO emissions due to a greater presence of microorganisms involved in NO production over those able to reduce NO. Significant differences in bacterial community composition between sites were observed, with the NO content being the main driver of these changes. Increased NO content in the sampling sites significantly reduced bacterial diversity. Bacterial genera involved in the degradation of organic and inorganic pollutants and nitrous oxide reduction, such as Robiginitalea, Symbiobacterium, Bacillus, Fusibacter, Neptunomonas, Colwellia, and Alteromonas, were the most abundant in the lagoon. The results suggest that the type of anthropogenic contamination directly impacts the nitrate content in the sediments of the Marchica lagoon, which determines variations in nitrous oxide emissions, nitrogen-cycling gene abundances, and bacterial diversity.

The genotypic and phenotypic diversity of nineteen bradyrhizobial strains isolated from the root nodules of wild-grown Cytisus villosus in the central-western region of the Moroccan Rif were carried out. PCR-based RFLP (restriction fragment length polymorphism) of the 16S rDNA (ARDRA) of 19 strains using the restriction enzymes AluI, CfoI, DdeI, HinfI, MspI and RsaI showed that they grouped in 3 clusters. The cluster I includes the type strain Bradyrhizobium canariense BTA-1, the cluster II the type strain Bradyrhizobium japonicum USDA6 and the cluster III the type strains Bradyrhizobium cytisi CTAW11 and Bradyrhizobium rifense CTAW71. The results from 63 physiological and biochemical tests confirmed the existence of the B. canariense and the B. japonicum groups but also allowed the separation of the B. cytisi and B. rifense strains in two groups. The phenotypic characteristics analysed permitted description of a wide physiological and biochemical diversity among the strains, and showed that the heavy metals resistance test was the most discriminating characteristic.

In this work we analyze through a polyphasic approach several Bradyrhizobium strains isolated in Venezuela from root nodules of Centrosema species. The analysis of the 16S rRNA gene showed that the strains belong to three clusters within genus Bradyrhizobium which have 100% similarity with Bradyrhizobium daqingense CCBAU 15774TBradyrhizobium guangxiense CCBAU 53363T and Bradyrhizobium viridifuturi SEMIA 690T. The results of recA and glnII gene analysis confirmed the identification of the strains CMVU02 and CMVU30 as Bradyrhizobium viridifuturi but the nodC gene analysis showed that they belong to a new symbiovar for which we propose the name tropici. Nevertheless, the concatenated recA and glnII gene phylogenetic analysis, DNA–DNA hybridization and phenotypic characterization showed that the strains A9T, CMVU44T and CMVU04 belong to two novel Bradyrhizobium species. The analysis of the nodC gene showed that these strains also represent two new symbiovars. Based on these results we propose the classification of the strain A9T isolated from Centrosema molle into the novel species Bradyrhizobium centrosemae (sv. centrosemae) sp. nov. (type strain A9T = LMG 29515T = CECT 9095T). and the classification of the strains CMVU44T and CMVU04 isolated from C. macrocarpum into the novel species Bradyrhizobium americanum (sv. phaseolarum) sp. nov. (type strain CMVU44T = LMG 29514T = CECT 9096T).

The presence of apothecia in mixed species (vegetatively reproducing lichens, occasionally producing ascomata) has been interpreted as a mechanism to increase genetic variability in mostly clonal populations. However, spore viability from these apothecia has not been studied. We asked whether ascospores of the mixed species Physconia grisea are viable and thereby contribute to increasing the genetic diversity within populations of this species. An ontogenetic study of spores in cultures of P. grisea and a related sexual species (P. distorta), showed that although mature apothecia from both species produced and discharged meiospores capable of germination, spores from P. grisea were only rarely (0.43 %) able to continue development whereas those from P. distorta germinated and developed successfully. The strongly reduced viability of P. grisea spores suggested that they do not have a strong reproductive function, at least in the two local populations analyzed. Additionally, we show that the segregation of Physconia grisea ssp. lilacina does not have molecular support. [Int Microbiol 2013; 16(3):145-155]Keywords: Physconia spp. · apothecia · sexual reproduction · germination · ontogenetic development · mixed species

In this paper we analyze through a polyphasic approach several Bradyrhizobium strains isolated in Spain and Morocco from root nodules of Retama sphaerocarpa and Retama monosperma. All the strains have identical 16S rRNA genes and their closest relative species is Bradyrhizobium lablabi CCBAU 23086T, with 99.41% identity with respect to the strain Ro19T. Despite the closeness of the 16S rRNA genes, the housekeeping genes recA, atpD and glnII were divergent in Ro19T and B. lablabi CCBAU 23086T, with identity values of 95.71%, 93.75% and 93.11%, respectively. These differences were congruent with DNA-DNA hybridization analysis that revealed an average of 35% relatedness between the novel species and B. lablabi CCBAU 23086T. Also, differential phenotypic characteristics of the new species were found with respect to the already described species of Bradyrhizobium. Based on the genotypic and phenotypic data obtained in this study, we propose to classify the group of strains isolated from R. sphaerocarpa and R. monosperma as a novel species named Bradyrhizobium retamae sp. nov. (type strain Ro19T=LMG 27393T=CECT 8261T). The analysis of symbiotic genes revealed that some of these strains constitute a new symbiovar within genus Bradyrhizobium for which we propose the name >retamae>, that mainly contains nodulating strains isolated from Retama species in different continents.