Rapid Detection of Serratia fonticola by TaqMan Quantitative Real-Time PCR Using Primers Targeting the gyrB Gene.

A gyrB gene is present in the majority of bacterial species, and encodes the ATPase domain of DNA gyraseB-subunit protein, which is essential for transcription and replication of bacteria. The gyrB gene exhibits higher nucleotide sequence variability than the 16S rDNA gene and thus could be more reliable in differentiating Serratia fonticola. A species-specific primer pair and probe were designed for quantitative real-time PCR detection of S. fonticola using gyrB as the target gene. Nine members of the Serratia family (representing nine Serratia species) were chosen to verify the specificity of the primers. Additionally, two species each of Salmonella and Klebsiella, and five other species belonging to five other genera of Enterobacteriaceae, were tested for primer cross-reaction. All the tested strains gave negative results. The limit of detection for S. fonticola using the gyrB gene was 100 copies per PCR reaction. This TaqMan PCR assay provided a specific, rapid, and sensitive method to detect S. fonticola based on its gyrB gene.

Simultaneous stimulation of glycolysis and gluconeogenesis by feeding in the anterior intestine of the omnivorous GIFT tilapia, Oreochromis niloticus.

The present study was performed to investigate the roles of anterior intestine in the postprandial glucose homeostasis of the omnivorous Genetically Improved Farmed Tilapia (GIFT). Sub-adult fish (about 173 g) were sampled at 0, 1, 3, 8 and 24 h post feeding (HPF) after 36 h of food deprivation, and the time course of changes in intestinal glucose transport, glycolysis, glycogenesis and gluconeogenesis at the transcription and enzyme activity level, as well as plasma glucose contents, were analyzed. Compared with 0 HPF (fasting for 36 h), the mRNA levels of both ATP-dependent sodium/glucose cotransporter 1 and facilitated glucose transporter 2 increased during 1-3 HPF, decreased at 8 HPF and then leveled off. These results indicated that intestinal uptake of glucose and its transport across the intestine to blood mainly occurred during 1-3 HPF, which subsequently resulted in the increase of plasma glucose level at the same time. Intestinal glycolysis was stimulated during 1-3 HPF, while glucose storage as glycogen was induced during 3-8 HPF. Unexpectedly, intestinal gluconeogenesis (IGNG) was also strongly induced during 1-3 HPF at the state of nutrient assimilation. The mRNA abundance and enzyme activities of glutamic-pyruvic and glutamic-oxaloacetic transaminases increased during 1-3 HPF, suggesting that the precursors of IGNG might originate from some amino acids. Taken together, it was concluded that the anterior intestine played an important role in the regulation of postprandial glucose homeostasis in omnivorous tilapia, as it represented significant glycolytic potential and glucose storage. It was interesting that postprandial IGNG was stimulated by feeding temporarily, and its biological significance remains to be elucidated in fish.