Influence of early rearing environment on water-borne cortisol and expression of stress-related genes in grass carp (Ctenopharyngodon idella)

Molecular Biology Reports - Nowadays, lower post-release survivorship of hatchery-reared fish in natural aquatic bodies has attained great attention and research is in progress to determine the...     

Evolution of Pseudomonas aeruginosa cells towards a filterable stage in seawater

In sterile nutrient-free seawater, the number of Pseudomonas aeruginosa culturable cells decreased progressively over time and the bacteria developed cells capable of passing through a 0.45 micron pore membrane. This development was more rapid in non-autoclaved, stirred seawater and the recovery of filterable cells varied depending on the membrane type used. Minicells were observed under an electron microscope. They yielded normal cells in bacteriological media with analogous colonies and an unchanged antibiotic resistance profile. Some biochemical characters, such as gelatinase or urease activity, were however modified in the filterable cells.     

Postmating Reproductive isolation between strains of Drosophila willistoni

Speciation can occur through the presence of reproductive isolation barriers that impede mating, restrict cross-fertilization, or render inviable/sterile hybrid progeny. The D. willistoni subgroup is ideally suited for studies of speciation, with examples of both allopatry and sympatry, a range of isolation barriers, and the availability of one species complete genome sequence to facilitate genetic studies of divergence. D. w. willistoni has the largest geographic distribution among members of the Drosophila willistoni subgroup, spanning from Argentina to the southern United States, including the Caribbean islands. A subspecies of D. w. willistoni, D. w. quechua, is geographically separated by the Andes mountain range and has evolved unidirectional sterility, in that only male offspring of D. w. quechua females × D. w. willistoni males are sterile. Whether D. w. willistoni flies residing east of the Andes belong to one or more D. willistoni subspecies remains unresolved. Here we perform fecundity assays and show that F1 hybrid males produced from crosses between different strains found in Central America, North America, and northern Caribbean islands are reproductively isolated from South American and southern Caribbean island strains as a result of unidirectional hybrid male sterility. Our results show the existence of a reproductive isolation barrier between the northern and southern strains and suggest a subdivision of the previously identified D. willistoni willistoni species into 2 new subspecies.     

Resuscitation and morphological alterations of <Emphasis Type="Italic">Salmonella bovismorbificans</Emphasis> cells under starvation in soil

Salmonella bovismorbificans, rare serovar, isolated from patient in Tunisia were incubated during 13 years in soil. After its resuscitation, the cells showed a biochemical profile completely inactive on Api 20E system. These cells recuperated their initial characters after 6 months of incubation in Tryptic Soy broth. The atomic force micrographs showed a reduction of the cells size and an evolution to coccoid-shapes. After resuscitation S. bovismorbificans cells recuperated their original rod shape. These cells showed an altered envelope. The resuscitate cells were identified by PCR following the amplification of the internal transcribed spacer (ITS) region of 16S–23S rRNA gene.     

Interspecific molecular variation of Tunisian complex Lolium perenne L. and Festuca arundinacea Schreb. based on the internal transcribed spacer locus (ITS)

To establish phylogenetic relationships and estimate the intra and interspecific divergence, the amplification and the sequencing of the internal transcribed spacers of ribosomal DNA (ITS = ITS1 + 5.8S + ITS2) were analyzed in Tunisian complex Lolium–Festuca DNA. These spacer regions have evolved mainly by point mutations. Results revealed a high level of polymorphism within studied species. Significant similarities were observed between these two species and showed the existence of an important phylogenetic relationship. Besides, this molecular approach has revealed two new clusterings, with a homologous ITS gene namely: Bromus hordeaceus and Hordeum murinum subsp. This could be explained by the conservation of an ancestral ITS gene in some fescue plants. Thus, Tunisian tall fescue and perennial ryegrass may derive from Bromus hordeaceus and Hordeum murinum subsp. Considerable morphology and bioclimatic distribution similarities were discovered in ITS sequences within the same species. This study can be of great help to identify suitable accessions that could be used in local fescue and ryegrass improvement program.