Archaeal Communities in a Heterogeneous Hypersaline-Alkaline Soil

In this study the archaeal communities in extreme saline-alkaline soils of the former lake Texcoco, Mexico, with electrolytic conductivities (EC) ranging from 0.7 to 157.2 dS/m and pH from 8.5 to 10.5 were explored. Archaeal communities in the 0.7 dS/m pH 8.5 soil had the lowest alpha diversity values and were dominated by a limited number of phylotypes belonging to the mesophilic Candidatus Nitrososphaera. Diversity and species richness were higher in the soils with EC between 9.0 and 157.2 dS/m. The majority of OTUs detected in the hypersaline soil were members of the Halobacteriaceae family. Novel phylogenetic branches in the Halobacteriales class were detected in the soil, and more abundantly in soil with the higher pH (10.5), indicating that unknown and uncharacterized Archaea can be found in this soil. Thirteen different genera of the Halobacteriaceae family were identified and were distributed differently between the soils. Halobiforma, Halostagnicola, Haloterrigena, and Natronomonas were found in all soil samples. Methanogenic archaea were found only in soil with pH between 10.0 and 10.3. Retrieved methanogenic archaea belonged to the Methanosarcinales and Methanomicrobiales orders. The comparison of the archaeal community structures considering phylogenetic information (UniFrac distances) clearly clustered the communities by pH

Identificación morfológica y filogenética de un consorcio microbiano fotosintético de posible interés biotecnológico

Background. Microbial consortia have ecological and biotechnological importance since they contribute to thebiogeochemical cycles in nature and produce compounds of high economical value. Goals. Research for this paperinvolved the polyphasic study of a photosynthetic microbial consortium (MC) in order to identify the microorganisms thatcomprise it, in addition to exploring the theory of the biotechnological potential of each partner within the consortium.Methods. Study of morphological and phylogenetic diversity. Results. Twenty-one different microorganisms wereidentified that make up the MC belonging to the phyla Proteobacteria (Rhodobacter sp., Devosia insulae, Pedomicrobiumamericanum, Alpha proteobacteria, Aquaspirillum delicatum, Methylibium petroleiphilum and Nannocystis sp.), Bacteriodetes (Flavobacterium sp. and Flavobacterium aquatile), Cyanobacteria (Aphanizomenon aphanizomenoides, Leptolyngbya sp. and Anabaena oscillarioides), Chlorophyta (Monoraphidium sp. and Chlorella sp.), Heterokontophyta (Cyclotella meneghiniana, Melosira varians, Cocconeis placentula, Achnanthidium chlidanos, Navicula radiosa, Fragilaria ulna and Nitzschia sp.). This microbial consortium was shown to have a high capacity for nitrogen fixation (10,294 nmol ethylene g-1 dry weight h-1). Conclusions. The identification of microorganisms that form the MC and their capacity for growth and nitrogen fixation in a photobioreactor, give us a glimpse of their possible biotechnological application as a biofertilizer.Antecedentes. Los consorcios microbianos son de importancia ecológica y biotecnológica por que contribuyen a los ciclosbiogeoquímicos y producen compuestos de alto valor añadido. Objetivos. Realizar el estudio polifásico de un consorciomicrobiano (CM) fotosintético, con el fin de identificar los microorganismos que lo integran, además del aporte teóricodel potencial biotecnológico de cada uno de ellos como parte del consorcio. Métodos. Se empleó un estudio de la diversidad morfológica y filogenética. Resultados. En el CM se identificaron 21 microorganismos diferentes pertenecientes a los phyla Proteobacteria (Rhodobacter sp., Devosia insulae, Pedomicrobium americanum, Alpha proteobacteria, Aquaspirillum delicatum, Methylibium petroleiphilum y Nannocystis sp.), Bacteroidetes (Flavobacterium sp. y Flavobacterium aquatile), Cyanobacteria (Aphanizomenon aphanizomenoides, Leptolyngbya sp. y Anabaena oscillarioides), Chlorophyta (Monoraphidium sp., Chlorella sp.), Heterokontophyta (Cyclotella meneghiniana, Melosira varians, Cocconeis placentula, Achnanthidium chlidanos, Navicula radiosa, Fragilaria ulna y Nitzschia sp.). Este consorcio microbiano ha mostrado tener una elevada capacidad de fijación de nitrógeno (10,294 nmoles etileno g-1 peso seco h-1). Conclusiones. La identificación de los microorganismos que conforman el CM, su capacidad de crecimiento y la fijación de nitrógeno en un fotobiorreactor, permiten vislumbrar su posible aplicación biotecnológica como biofertilizante

The bacterial community structure in an alkaline saline soil spiked with anthracene

Background: The application of polycyclic aromatic hydrocarbons (PAHs) will affect the bacterial community structure as some groups will be favoured and others not. An alkaline saline soil with electrolytic conductivity (EC) 56 dS m-1 was spiked with anthracene and acetone while their effect on bacterial community structure was investigated. Results: The percentages of Acidobacteria and Actinobacteria decreased over time, while the percentage of Proteobacteria, mostly Xanthomonadales, increased. The percentage of the phylotypes belonging to the Nocardioides , Rhodococcus and Streptomyces , known degraders of PAHs, was larger in the anthracene-amended soil than in the acetone-amended and unamended soil at day 14. The phylotypes belonging to the genera Sphingomonas , also a known degrader of PAHs, however, was lower. Weighted and unweighted PCoA with UniFrac indicated that phylotypes were similar in the different treatments at day 0, but changed at day 1. After 14 days, phylotypes in the unamended and acetone-amended soil were similar, but different from those in the anthracene-spiked soil. Conclusions: It was found that incubating the soil and contaminating it with anthracene changed the bacterial community structure, but spiking the soil with acetone had little or no effect on the bacterial community structure compared to the unamended soil

Genetic Diversity in Pseudomonas syringae pv. maculicola Strains

Pseudomonas syringae pv. maculicola (Psm) is a phytopathogen of a wide range of host plants from the cruciferae family, producing blight. Some strains infect Arabidopsis thaliana, whose genetic characteristics has made it a plant model for analyses of different process, such as resistance to phytopathogens. In this study, we have focused on this bacterium in order to understand how plant-pathogen interactions influence its genome organization. Eight strains of Pseudomonas syringae pv. maculicola were selected and analyzed by RFLP using PacI and PmeI restriction enzymes in order to evaluate the conservation of the number and size of the restriction fragment into the strains. The results show heterogeneity in the structure and composition of the Psm genome. This heterogeneity has not a clearly relationship between the production of coronatine and the presence/absence or copy number of plasmids., The genome dynamics could be related with the pathogenicity island even the genome origin

The potential of cold-shock promoters for the expression of recombinant proteins in microbes and mammalian cells

Abstract Background Low-temperature expression of recombinant proteins may be advantageous to support their proper folding and preserve bioactivity. The generation of expression vectors regulated under cold conditions can improve the expression of some target proteins that are difficult to express in different expression systems. Main body of the abstract The cspA encodes the major cold-shock protein from Escherichia coli (CspA). The promoter of cspA has been widely used to develop cold shock-inducible expression platforms in E. coli. Moreover, it is often necessary to employ expression systems other than bacteria, particularly when recombinant proteins require complex post-translational modifications. Currently, there are no commercial platforms available for expressing target genes by cold shock in eukaryotic cells. Consequently, genetic elements that respond to cold shock offer the possibility of developing novel cold-inducible expression platforms, particularly suitable for yeasts, and mammalian cells. Conclusions This review covers the importance of the cellular response to low temperatures and the prospective use of cold-sensitive promoters to direct the expression of recombinant proteins. This concept may contribute to renewing interest in applying white technologies to produce recombinant proteins that are difficult to express. Graphical Abstrac