Isolation and Identification of Two Brucella Species from a Volcanic Lake in Mexico.

Brucellosis is a zoonosis caused by bacteria of the Brucella genus. Any source of contamination that could be infectious must be monitored to reduce the risk of exposure to brucellosis, so the purpose of this work was to determine the presence of Brucella spp. on surface water and tilapia (Oreochromis niloticus) skin from a volcanic lake in Mexico. A seasonal sampling during 2016-2017 was carried out at fifteen specific sites for water sampling and five sites for the collection of tilapia fish. From all water and fish samples tested, we found only three isolates of Brucella species. We isolated and identified B. abortus from surface water through bacteriological and molecular techniques, and B. abortus and B. suis from the same tilapia skin sample. The isolated strains likely came from breeding animals that are common to the region, such as infected pigs or cattle with Brucella abortus or B. suis, respectively. A similar finding has not been reported in a water from volcanic lake or tilapia fish in Mexico. We concluded that B. abortus and B. suis are present on the surface water of the volcanic lake and tilapia skin as possible contaminants derived from biological material from cows and pigs carrying this bacterium.

In Silico Analysis of the Structural and Biochemical Features of the NMD Factor UPF1 in Ustilago maydis.

The molecular mechanisms regulating the accuracy of gene expression are still not fully understood. Among these mechanisms, Nonsense-mediated Decay (NMD) is a quality control process that detects post-transcriptionally abnormal transcripts and leads them to degradation. The UPF1 protein lays at the heart of NMD as shown by several structural and functional features reported for this factor mainly for Homo sapiens and Saccharomyces cerevisiae. This process is highly conserved in eukaryotes but functional diversity can be observed in various species. Ustilago maydis is a basidiomycete and the best-known smut, which has become a model to study molecular and cellular eukaryotic mechanisms. In this study, we performed in silico analysis to investigate the structural and biochemical properties of the putative UPF1 homolog in Ustilago maydis. The putative homolog for UPF1 was recognized in the annotated genome for the basidiomycete, exhibiting 66% identity with its human counterpart at the protein level. The known structural and functional domains characteristic of UPF1 homologs were also found. Based on the crystal structures available for UPF1, we constructed different three-dimensional models for umUPF1 in order to analyze the secondary and tertiary structural features of this factor. Using these models, we studied the spatial arrangement of umUPF1 and its capability to interact with UPF2. Moreover, we identified the critical amino acids that mediate the interaction of umUPF1 with UPF2, ATP, RNA and with UPF1 itself. Mutating these amino acids in silico showed an important effect over the native structure. Finally, we performed molecular dynamic simulations for UPF1 proteins from H. sapiens and U. maydis and the results obtained show a similar behavior and physicochemical properties for the protein in both organisms. Overall, our results indicate that the putative UPF1 identified in U. maydis shows a very similar sequence, structural organization, mechanical stability, physicochemical properties and spatial organization in comparison to the NMD factor depicted for Homo sapiens. These observations strongly support the notion that human and fungal UPF1 could perform equivalent biological activities.