Carmen M. González-Domenech

Halomonas cerina sp. nov., a moderately halophilic, denitrifying, exopolysaccharide-producing bacterium.

Three bacterial strains were isolated from different saline soils in Spain. The novel strains were moderately halophilic, exopolysaccharide-producing, Gram-negative, non-motile rods. The strains required NaCl and grew best with 7.5-10 % (w/v) NaCl in the medium. They formed wax-coloured colonies, were oxidase-positive and showed respiratory metabolism, using oxygen, nitrate and nitrite as terminal electron acceptors. The novel strains were able to denitrify and did not produce acid from sugars. The DNA G+C contents varied between 62.7 and 66.2 mol%. Phylogenetic analyses based on 16S rRNA gene sequences and sequence signatures of this gene showed that all three novel isolates belonged to the genus Halomonas in the class Gammaproteobacteria and formed an independent phylogenetic line. The most phylogenetically related species were Halomonas alimentaria, Halomonas campaniensis, Halomonas gudaonensis and Halomonas ventosae, with which the novel strains showed 16S rRNA gene sequence similarity values of between 96.3 and 95.2 %. The principal fatty acids of the novel strains were 16 : 0, 18 : 1 omega 7c, 16 : 1 omega 7c and 19 : 0 cyclo omega 8c. The predominant respiratory lipoquinone was ubiquinone with nine isoprene units (Q-9). The name Halomonas cerina sp. nov. is proposed for these isolates. The type strain is SP4T (=CECT 7282T=LMG 24145T).

Metabolic stasis in an ancient symbiosis: genome-scale metabolic networks from two Blattabacterium cuenoti strains, primary endosymbionts of cockroaches

BackgroundCockroaches are terrestrial insects that strikingly eliminate waste nitrogen as ammonia instead of uric acid. Blattabacterium cuenoti (Mercier 1906) strains Bge and Pam are the obligate primary endosymbionts of the cockroaches Blattella germanica and Periplaneta americana, respectively. The genomes of both bacterial endosymbionts have recently been sequenced, making possible a genome-scale constraint-based reconstruction of their metabolic networks. The mathematical expression of a metabolic network and the subsequent quantitative studies of phenotypic features by Flux Balance Analysis (FBA) represent an efficient functional approach to these uncultivable bacteria.ResultsWe report the metabolic models of Blattabacterium strains Bge (iCG238) and Pam (iCG230), comprising 296 and 289 biochemical reactions, associated with 238 and 230 genes, and 364 and 358 metabolites, respectively. Both models reflect both the striking similarities and the singularities of these microorganisms. FBA was used to analyze the properties, potential and limits of the models, assuming some environmental constraints such as aerobic conditions and the net production of ammonia from these bacterial systems, as has been experimentally observed. In addition, in silico simulations with the iCG238 model have enabled a set of carbon and nitrogen sources to be defined, which would also support a viable phenotype in terms of biomass production in the strain Pam, which lacks the first three steps of the tricarboxylic acid cycle. FBA reveals a metabolic condition that renders these enzymatic steps dispensable, thus offering a possible evolutionary explanation for their elimination. We also confirm, by computational simulations, the fragility of the metabolic networks and their host dependence.ConclusionsThe minimized Blattabacterium metabolic networks are surprisingly similar in strains Bge and Pam, after 140 million years of evolution of these endosymbionts in separate cockroach lineages. FBA performed on the reconstructed networks from the two bacteria helps to refine the functional analysis of the genomes enabling us to postulate how slightly different host metabolic contexts drove their parallel evolution.

Halomonas fontilapidosi sp. nov., a moderately halophilic, denitrifying bacterium

We have made a polyphasic taxonomic study of strain 5CR(T), isolated from Fuente de Piedra, Málaga, southern Spain. The strain is a moderately halophilic, Gram-negative rod, oxidase-positive and motile by a single polar flagellum. It does not produce acids from sugars and shows respiratory metabolism, using oxygen, nitrate and nitrite as terminal electron acceptors. It requires NaCl and grows best with 5-7.5 % w/v at temperatures of between 32 and 45 degrees C within a pH range of 6-8. Its 16S rRNA gene sequence indicates that strain 5CR(T) belongs to the genus Halomonas in the class Gammaproteobacteria. Its closest relatives are Halomonas alimentaria, H. nitroreducens, H. shengliensis and H. ventosae, with the type strains of which our strain showed 16S rRNA gene sequence similarity values of 96.7-97.8 %. DNA-DNA hybridization studies between strain 5CR(T) and H. ventosae CECT 5797(T), the phylogenetically nearest type strain, showed 40 % relatedness. Its G+C content is 65.7 mol%. Its major fatty acids are C(18 : 1)omega7c (31.36 %), C(16 : 0) (25.55 %), C(16 : 1)omega7c/iso-C(15 : 0) 2-OH (23.23 %), C(19 : 0) cyclo omega8c (8.14 %), C(12 : 0) 3-OH (5.76 %) and C(10 : 0) (2.22 %) and the predominant respiratory lipoquinone is ubiquinone with nine isoprene units (Q-9). The proposed name for the novel species is Halomonas fontilapidosi sp. nov., strain 5CR(T) (=CECT 7341(T) =LMG 24455(T)) being the type strain.

Halomonas nitroreducens sp. nov., a novel nitrate-and nitrite-reducing species

We have carried out a polyphasic taxonomic study of strain 11ST, a halophilic, Gram-negative bacterium that is able to respire on nitrate and nitrite in anaerobiosis. Strain 11ST was isolated from a solar saltern in Cahuil, a region next to Pichilemu (Chile). It grows at NaCl concentrations within the range of 3-20 % w/v (optimum 5-7.5 %), temperatures from 4 to 45 degrees C (optimum 20-32 degrees C) and within a pH range of 5-10 (optimum pH 7-9). Its 16S rRNA gene sequence indicates that it belongs to the genus Halomonas in the class Gammaproteobacteria. Its closest relatives are Halomonas alimentaria, H. denitrificans, H. organivorans and H. ventosae, with the type strains of which our strain showed maximum 16S rRNA gene sequence similarity values of 97.1-98.1 %. Its G+C content is 65.3 mol%. DNA-DNA hybridization studies showed 54.2 % relatedness between strain 11ST and H. alimentaria DSM 15356T and 47.2 % relatedness between strain 11ST and H. organivorans CECT 5995T. Lower DNA-DNA hybridization percentages were obtained against the type strains of other related Halomonas species. Its major fatty acids are C12 : 0 3-OH (5.56 %), iso-C15 : 0 2-OH/C16 : 1 omega 7c (22.30 %), C16 : 0 (27.80 %) and C18 : 1 omega 7c (29.92 %). The proposed name for the novel species is Halomonas nitroreducens sp. nov., with strain 11ST (=CECT 7281T =LMG 24185T) being the type strain.

Denitrification as an important taxonomic marker within the genus Halomonas.

We have made a comprehensive study of the denitrifying species of the genus Halomonas, evaluating both the phylogenetic and phenotypic relationships amongst them and other species of Halomonas. The phylogenetic analysis was based on the 16S rRNA gene sequence as well as those of the three genes essential to a complete denitrification process: narH, nirS and nosZ. The main aim of the phenotypic study was to improve our knowledge of some of the species in question. To this end we investigated the type strain of each species, although in the case of Halomonas cerina we also studied strains R53 and 15CR. In addition to this we investigated some other strains phylogenetically related to Halomonas ventosae, Halomonas denitrificans and Halomonas koreensis that were isolated during this study. We also looked into the conditions under which all these bacteria denitrify. Our results indicate that these denitrifying species of Halomonas are all closely related. A numerical analysis of the phenotypic data demonstrates a high phenotypic similarity (73%) between most of them. In addition, all the denitrifying strains have a high G+C content of between 63 and 74.3 mol%. The results of the phylogenetic study point to two evolutionary lineages for the process. Although phenotypic similarity does not always reflect phylogenetic relatedness, we have found significant congruence between both features in Halomonas, making it clear that denitrifying ability should be considered as an important phenotypic and phylogenetic discriminatory marker within this genus.

Blueprint for a minimal photoautotrophic cell: conserved and variable genes in Synechococcus elongatus PCC 7942

BackgroundSimpler biological systems should be easier to understand and to engineer towards pre-defined goals. One way to achieve biological simplicity is through genome minimization. Here we looked for genomic islands in the fresh water cyanobacteria Synechococcus elongatus PCC 7942 (genome size 2.7 Mb) that could be used as targets for deletion. We also looked for conserved genes that might be essential for cell survival.ResultsBy using a combination of methods we identified 170 xenologs, 136 ORFans and 1401 core genes in the genome of S. elongatus PCC 7942. These represent 6.5%, 5.2% and 53.6% of the annotated genes respectively. We considered that genes in genomic islands could be found if they showed a combination of: a) unusual G+C content; b) unusual phylogenetic similarity; and/or c) a small number of the highly iterated palindrome 1 (HIP1) motif plus an unusual codon usage. The origin of the largest genomic island by horizontal gene transfer (HGT) could be corroborated by lack of coverage among metagenomic sequences from a fresh water microbialite. Evidence is also presented that xenologous genes tend to cluster in operons. Interestingly, most genes coding for proteins with a diguanylate cyclase domain are predicted to be xenologs, suggesting a role for horizontal gene transfer in the evolution of Synechococcus sensory systems.ConclusionsOur estimates of genomic islands in PCC 7942 are larger than those predicted by other published methods like SIGI-HMM. Our results set a guide to non-essential genes in S. elongatus PCC 7942 indicating a path towards the engineering of a model photoautotrophic bacterial cell.

Lipid changes in HIV-patients switching to the coformulated single tablet FTC/RPV/TDF (Eviplera®). Efficacy and safety analysis. GeSida Study 8114

Rilpivirine (RPV) has a better lipid profile than efavirenz (EFV) in naïve patients [ 1 ]. Switching to RPV may be convenient for many patients, while maintaining a good immunovirological control [ 2 ]. The aim of this study was to analyze lipid changes in HIV‐patients at 24 weeks after switching to Eviplera® (emtricitabine/RPV/tenofovir disoproxil fumarate [FTC/RPV/TDF]).

Safety and Efficacy of Dolutegravir Plus Rilpivirine in Treatment-Experienced HIV-Infected Patients: The DORIVIR Study:

Objectives: To analyze the efficacy and safety of dolutegravir/rilpivirine (DTG/RPV) in HIV-infected patients who switched from any other antiretroviral therapy (ART). Methods: Open-label, multicenter study including patients who switched to DTG/RPV between February 2015 and February 2016. Efficacy (HIV RNA <50 copies/mL), adverse events, and metabolic changes at 24 weeks were analyzed. Results: A total of 104 participants were included, who switched for the following reasons: toxicity/intolerance (42.3%), convenience (27.8%), and drug interactions (17.3%). Prior regimens are protease inhibitor (56.7%), integrase strand transfer inhibitor (26.9%), and non-nucleoside reverse transcriptase inhibitor (16.3%). Efficacy at 24 weeks was 88.4% (intention to treat) and 96.8% (per protocol). Triglyceride levels were reduced, on average, by 12.7% and a mean decrease of 9.0% in the glomerular filtration rate was observed as well (P values of .003 and .002, respectively), whereas total cholesterol, HDL cholesterol, LDL cholesterol, creatinine, and glutamic-pyruvic transaminase remained unchanged. No patient discontinued due to adverse events. Conclusions: Dolutegravir/RPV is effective and safe in long-term HIV-infected patients under any prior ART. Toxicity, convenience, and interactions were the main reasons for changing. At 24 weeks, the lipid profile improved with a decrease in triglycerides.

Emergence as an outbreak of the HIV-1 CRF19_cpx variant in treatment-naïve patients in southern Spain

Background CRF19_cpx is a complex circulating recombination form (CRF) of HIV-1. We describe the characteristics of an outbreak of the CRF19_cpx variant among treatment-naïve patients in southern Spain. Methods The study was undertaken at the Virgen de la Victoria Hospital, a reference centre for the analysis of HIV-1 genotype in Malaga (Spain). Subtyping was performed through REGA v3.0 and the relationship of our CRF19_cpx sequences, among themselves and regarding other reference sequences from the same variant, was defined by phylogenetic analysis. We used PhyML program to perform a reconstruction of the phylogeny by Maximum Likelihood method as well as further confirmation of the transmission clusters by Bayesian inference. Additionally, we collected demographic, clinical and immunovirological data. Results Between 2011 and 2016, we detected 57 treatment-naïve patients with the CRF19_cpx variant. Of these, 55 conformed a very well-defined transmission cluster, phylogenetically close to CRF19_cpx sequences from the United Kingdom. The origin of this subtype in Malaga was dated between 2007 and 2010. Over 50% of the patients presented the non-nucleoside reverse transcriptase inhibitor G190A resistance mutation. This variant was mostly represented by young adult Spanish men who had sex with men. Almost half of them were recent seroconverters, though a similar percentage was diagnosed at a late state of HIV infection. Five cases of AIDS and one non-AIDS defined death occurred during follow-up. The majority of patients treated with first-line combination antiretroviral therapy (ART) responded. Conclusions We report the largest HIV-1 CRF19_cpx cohort of treatment-naïve patients outside Cuba, almost all emerging as an outbreak in the South of Spain. Half the cases had the G190A resistance mutation. Unlike previous studies, the variant from Malaga seems less pathogenic, with few AIDS events and an excellent response to ART.

Identification of Xenologs and Their Characteristic Low Expression Levels in the Cyanobacterium Synechococcus elongatus

Horizontal gene transfer (HGT) is a central process in prokaryotic evolution. Once a gene is introduced into a genome by HGT, its contribution to the fitness of the recipient cell depends in part on its expression level. Here we show that in Synechococcus elongatus PCC 7942, xenologs derived from non-cyanobacterial sources exhibited lower expression levels than native genes in the genome. In accord with our observation, xenolog codon adaptation indexes also displayed relatively low expression values. These results are in agreement with previous reports that suggested the relative neutrality of most xenologs. However, we also demonstrated that some of the xenologs detected participated in cellular functions, including iron starvation acclimation and nitrate reduction, which corroborate the role of HGT in bacterial adaptation. For example, the expression levels of some of the xenologs detected are known to increase under iron-limiting conditions. We interpreted the overall pattern as an indication that there is a selection pressure against high expression levels of xenologs. However, when a xenolog protein product confers a selective advantage, natural selection can further modulate its expression level to meet the requirements of the recipient cell. In addition, we show that ORFans did not exhibit significantly lower expression levels than native genes in the genome, which suggested an origin other than xenology.