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Streptococci obtained from rumen sources were tested for the production of antibacterial compounds using a deferred-antagonism plating assay. Of 35 isolates tested, 7 were identified that inhibited the growth of other streptococci. None of the inhibitory activity was due to bacteriophage. Three isolates, LRC0253, LRC0255, and LRC0476, were selected for further characterization. Analysis of 16S ribosomal DNA indicated that LRC0476 was a strain of Streptococcus bovis, while isolates LRC0253 and LRC0255 are likely strains of Streptococcus gallolyticus. The antibacterial compounds produced by these bacteria were protease sensitive, remained active in a pH range from 1 to 12, and did not lose activity after heating at 100°C for 15 min. The inhibitory peptide from strain LRC0255 was purified using pH-dependent adsorption and desorption to bacterial cells, followed by ammonium sulfate precipitation and reversed-phase chromatography and gel filtration. The peptide was 6 kDa, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. An oligonucleotide probe based on the N-terminal sequence of the purified peptide was used to identify the gene encoding the inhibitory peptide. The antibacterial peptide has characteristics that are very similar to those described for class II bacteriocins of gram-positive bacteria.Bacteriocins are a heterogeneous group of antibacterial peptides and proteins characterized by their ability to inhibit closely related, and sometimes more distantly related, strains of bacteria (10). It has been proposed that bacteriocins may play a key role in bacterial population dynamics (25). In particular, the bacteriocin may give the producing strains a competitive advantage by killing bacteria in the same environment competing for the same resources (23). The diversity and density of the microbial population of the rumen suggest that this environment might favor the evolution of bacteriocins as competitive factors (11,22). If this can be confirmed, bacteriocins would have potential applications as agents for the modification of rumen microbial populations (13, 30). However, the frequency and significance of bacteriocins in the rumen ecosystem is only starting to be examined.Bacteriocin-like inhibitory substances (BLIS) have been detected in several genera of rumen bacteria, including Streptococcus bovis (9), staphylococci isolated from preruminant calves and lambs (16), Enterococcus faecium (17, 18), Ruminococcus albus (4,22), and Butyrivibrio fibrisolvens (13). BLIS from two strains of B. fibrisolvens have been purified and characterized. The inhibitors were small, hydrophic peptides similar to lantibiotic (12) and nonlantibiotic (13) bacteriocins of gram-positive bacteria. To date, the two bacteriocins from B. fibrisolvens strains are the only BLIS from rumen bacteria to be confirmed as bacteriocins.The predominant streptococcus isolated from the rumen of animals is S. bovis. S. bovis is a highly amylolytic, fast-growing, acid-tolerant, gram-positive bacterium, fermenting starch primari...

Human erythrocyte membranes metabolize inositol 1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P4] to inositol 1,3,4-trisphosphate [Ins(1,3,4)P3] in the presence of Mg2+. In the absence of Mg2+ a less rapid conversion of Ins(1,3,4,5)P4 into Ins(1,4,5)P3 was revealed. Such an enzyme activity, if present in hormonally sensitive cells, could provide a mechanism for maintaining constant concentrations of Ins(1,4,5)P3 and Ins(1,3,4,5)P4, important for stimulation of Ca2+ entry after Ca2+ mobilization.

Detection of cystic fibrosis transmembrane conductance regulator (CFTR) protein is usually a difficult task to accomplish due to the low levels of expression and high turnover that this membrane protein is submitted to in the cell. Common biochemical methods can be used for the detection of CFTR but several critical points must be taken into account. The scope of this article is to outline biochemical methods commonly used to assess CFTR expression, processing and membrane localization.