Microbial composition of Saharan dust plumes deposited as red rain in Granada (Southern Spain)

During durst storms, also biological material is transported from arid areas such as the Sahara Desert. In the present work, rain samples containing significant amounts of mineral dust have been collected in Granada during different red rain episodes. Biological features (bacteria, biofilm, pollen grain and fungal spore) as well as size-particle distribution and mineralogical composition were studied by SEM. Nanobacteria were observed for the first time in red rain samples. A preliminary metabarcoding analysis was performed on three red rain samples. Here, Bacillota made up 18 % and Pseudomonadota 23 % of the whole prokaryotic community. The fungal community was characterized by a high abundance of Ascomycota and, dependent on the origin, the presence of Chytridiomycota. By means of 16S rRNA sequencing, 18 cultivable microorganisms were identified. In general, members of the phyla Pseudomonadota and Bacillota made up the majority of taxa. Some species, such as Peribacillus frigoritolerans and Bacillus halotolerans were isolated during three different red rain episodes. Generally, red rain carries a wide variety of microorganisms, being their ecosystem and health effects largely unknown.

[MEDICAGO SATIVA L: IMPROVEMENT AND NEW APPROACHES OF ITS NUTRITIONAL AND FUNCTIONAL VALUE BY BACTERIAL CO-INOCULATION]

OBJECTIVE

to study the effect of co-inoculation with Ensifer meliloti and Halomonas maura of the leguminous Medicago sativa L., on growth, nutritional and functional value, grown under salinity conditions.

METHODS

plants of M. sativa were grown in a solution with a mixture of salts (CaSO4, MgCl, NaCl and NaHCO 3) and were co-inoculated with its specific rhizobium and the halophilic moderated bacterium H. maura. Different physiologic parameters were determined, as well as, nitrogen and minerals content. Furthermore, an assay of in vitro digestibility was carried out.

RESULTS

salinity had a negative effect on the plants; however, co-inoculation increased yield, nitrogen content, total minerals, Ca and Mg. Moreover, physiologic parameters as water potential and leghemoglobin content in fresh nodules were higher compared to those of plants inoculated only with E. meliloti. Both, salinity and bacterial treatment with E. meliloti and H. maura increased the antioxidant capacity of the legume, in dialyzates and retentates collected after an in vitro digestibility assay.

CONCLUSION

co-inoculation of plants with E. meliloti and H. maura could improve the alfalfa yield under specific salinity conditions, increasing the nutritional and functional value of the plants. M. sativa could be considered in the formulations of nutritional supplements for the human diet.

Alteromonas hispanica sp. nov., a polyunsaturated-fatty-acid-producing, halophilic bacterium isolated from Fuente de Piedra, southern Spain

Strain F-32T, which produces exopolysaccharides and contains polyunsaturated fatty acids, was isolated from a hypersaline water sample collected from Fuente de Piedra (southern Spain). Phylogenetic analyses indicated conclusively that the strain in question belonged to the genus Alteromonas. Phenotypic tests showed that it could be assigned to the genus Alteromonas although it had a number of distinctive characteristics: it is moderately halophilic, growing best with 7·5–10 % w/v NaCl; it grows at 4 °C and produces H2S; it does not grow with d-cellobiose, d-fructose, d-galactose, d-glucose or lactose as sole sources of carbon and energy; and its fatty-acid profile is typical of Alteromonas but it also contains a large amount of an unusual acid with three double bonds [18 : 3ω6c (6, 9, 12); 5·01 %, w/v]. The major isoprenoid quinone is Q8. The DNA G+C content is 46·3 mol%. The phylogenetic, phenotypic and genetic properties of strain F-32T place it within a novel species, for which the name Alteromonas hispanica sp. nov. is proposed. The type strain is F-32T (=CECT 7067T=LMG 22958T).

epsABCJ genes are involved in the biosynthesis of the exopolysaccharide mauran produced by Halomonas maura

The moderately halophilic strainHalomonas mauraS-30 produces a high-molecular-mass acidic polymer (4·7×106 Da) composed of repeating units of mannose, galactose, glucose and glucuronic acid. This exopolysaccharide (EPS), known as mauran, has interesting functional properties that make it suitable for use in many industrial fields. Analysis of the flanking regions of a mini-Tn5insertion site in an EPS-deficient mutant ofH. maura, strain TK71, led to the identification of five ORFs (epsABCDJ), which form part of a gene cluster (eps) with the same structural organization as others involved in the biosynthesis of group 1 capsules and some EPSs. Conserved genetic features were found such as JUMPstart andopselements, which are characteristically located preceding the gene clusters for bacterial polysaccharides. On the basis of their amino-acid-sequence homologies, their putative hydropathy profiles and the effect of their mutations, it is predicted that EpsA (an exporter-protein homologue belonging to the OMA family) and EpsC (a chain-length-regulator homologue belonging to the PCP family) play a role in the assembly, polymerization and translocation of mauran. The possibility that mauran might be synthesized via a Wzy-like biosynthesis system, just as it is for many other polysaccharides, is also discussed. This hypothesis is supported by the fact that EpsJ is homologous with some members of the PST-exporter-protein family, which seems to function together with each OMA–PCP pair in polysaccharide transport in Gram-negative bacteria, transferring the assembled lipid-linked repeating units from the cytoplasmic membrane to the periplasmic space. Maximum induction of theepsgenes is reached during stationary phase in the presence of 5 % (w/v) marine salts.

Salipiger mucescens gen. nov., sp. nov., a moderately halophilic, exopolysaccharide-producing bacterium isolated from hypersaline soil, belonging to the α-Proteobacteria

Salipiger mucescens gen. nov., sp. nov. is a moderately halophilic, exopolysaccharide-producing, Gram-negative rod isolated from a hypersaline habitat in Murcia in south-eastern Spain. The bacterium is chemoheterotrophic and strictly aerobic (i.e. unable to grow under anaerobic conditions either by fermentation or by nitrate or fumarate respiration). It does not synthesize bacteriochlorophyll a. Catalase and phosphatase are positive. It does not produce acids from carbohydrates. It cannot grow with carbohydrates or amino acids as sole sources of carbon and energy. It grows best at 9–10 % w/v NaCl and requires the presence of Na+ but not Mg2+ or K+, although they do stimulate its growth somewhat when present. Its major fatty-acid component is 18 : 1ω7c (78·0 %). The predominant respiratory lipoquinone found in strain A3T is ubiquinone with ten isoprene units. The G+C content is 64·5 mol%. Phylogenetic analyses strongly indicate that this strain forms a distinct line within a clade containing the genus Roseivivax in the subclass α-Proteobacteria. The similarity value with Roseivivax halodurans and Roseivivax halotolerans is 94 %. In the light of the polyphasic evidence gathered in this study it is proposed that the isolate be classified as representing a new genus and species, Salipiger mucescens gen. nov., sp. nov. The proposed type strain is strain A3T (=CECT 5855T=LMG 22090T=DSM 16094T).