Bacteriology of the oral cavity of BALB/c mice

To be used as a model in dental research, an animal must fulfil experimental needs and information on the composition and variation of its oral flora must be available. Only limited data are available on the indigenous oral bacterial flora of BALB/c mice. In this work, a total of 671 isolates from different sites (saliva, tongue, teeth, and mucosa) of the oral cavity of BALB/c mice were identified. Only 18 different species were isolated, which indicates the relative simplicity of the flora. The predominant species of the total cultivable flora were "Lactobacillus murinus" (38%), Staphylococcus aureus (37%), Streptococcus faecalis (8%), Staphylococcus sciuri (4%), and Escherichia coli (3%). The other species each represent less than 2% of the flora. "Lactobacillus murinus" is found in greater proportion on mucosa than in the other sites, Staph. aureus predominates in saliva, and Strep. faecalis was found in greater proportion in tooth samples. Statistical analyses, using the minimum percentage of similarity, indicate that there is some variation among the microflora of different mice but that this difference is smaller for mice from the same lot. These results set the basis for the study of the variations of the indigenous oral microflora of BALB/c mice under different conditions.     

Identification of strains isolated as total and fecal coliforms and comparison of both groups as indicators of fecal pollution in tropical climates

This study was undertaken to better characterize the groups of total coliforms (TC) and fecal coliforms (FC) and to evaluate both groups as indicators of fecal contamination of drinking well water in a tropical climate (The Ivory Coast, West Africa). Isolated colonies obtained as TC or FC on membrane filters were identified using the API-20E system. From the well water samples, 58 golden-green colonies with a metallic sheen isolated on Endo medium (TC) were identified as Escherichia coli (55%), Enterobacter (26%), Klebsiella (14%), Proteus (3%), and Citrobacter (2%). Among 132 colonies isolated on Endo medium as non-TC (not showing the characteristic golden metallic sheen), 10% were identified as E. coli. The 196 blue colonies isolated on M-FC medium at 44.5 degrees C (FC) were identified as E. coli (66%), Klebsiella (12%), Enterobacter (10%), Citrobacter (5%), Salmonella (3%), Serratia (3%), Proteus (2%), and Yersinia (0.5%). Among 24 nonblue colonies on M-FC medium, none were identified as E. coli. Of the colonies isolated from human feces, E. coli represents 92% of the TC and 89% of the FC. Although these results are limited, they tend to confirm the greater specificity of the fecal coliform technique over that of total coliform for the detection of fecal contamination of untreated well water. From the results presented here and the observations of other workers, it is suggested that the use of FC instead of TC should be considered as the method of choice for determining drinking water pollution of untreated groundwater supplies.     

Tyrosine phosphorylation of DEPTOR functions as a molecular switch to activate mTOR signaling

Metabolic dysfunction is a major driver of tumorigenesis. The serine/threonine kinase mechanistic target of rapamycin (mTOR) constitutes a key central regulator of metabolic pathways promoting cancer cell proliferation and survival. mTOR activity is regulated by metabolic sensors as well as by numerous factors comprising the phosphatase and tensin homolog/PI3K/AKT canonical pathway, which are often mutated in cancer. However, some cancers displaying constitutively active mTOR do not carry alterations within this canonical pathway, suggesting alternative modes of mTOR regulation. Since DEPTOR, an endogenous inhibitor of mTOR, was previously found to modulate both mTOR complexes 1 and 2, we investigated the different post-translational modification that could affect its inhibitory function. We found that tyrosine (Tyr) 289 phosphorylation of DEPTOR impairs its interaction with mTOR, leading to increased mTOR activation. Using proximity biotinylation assays, we identified SYK (spleen tyrosine kinase) as a kinase involved in DEPTOR Tyr 289 phosphorylation in an ephrin (erythropoietin-producing hepatocellular carcinoma) receptor–dependent manner. Altogether, our work reveals that phosphorylation of Tyr 289 of DEPTOR represents a novel molecular switch involved in the regulation of both mTOR complex 1 and mTOR complex 2.