This study tested the hypothesis that S. mutans biofilm-detached cells exhibit distinct physiological properties compared

with their sessile and planktonic counterparts. Biofilm-detached cells showed a longer generation time of 2.85 h compared with planktonic cells (2.06 h), but had higher phosphotransferase activity for sucrose and mannose (P < 0.05). Compared with planktonic cells, they showed higher chlorhexidine (CHX) resistance and fourfold more adherent (P < 0.05). Increased mutacin IV production in biofilm-detached cells was noted by a larger inhibition zone against Streptococcus gordonii (31.07 ± 1.62 mm Target Selective Inhibitor Library screening vs. 25.2 ± 1.74 mm by planktonic cells; P < 0.05). The expressions of genes associated with biofilm formation (gtfC and comDE) and mutacin (nlmA) were higher compared with planktonic cells (P < 0.05). In many properties, biofilm-detached cells shared similarity with sessile cells except for a higher phosphotransferase activity for sucrose, glucose, and mannose, increased resistance to CHX, and elevated expression of gtfC-, comDE-, and acidurity-related gene aptD (P < 0.05). Based on data obtained, the S. mutans biofilm-detached cells are partially distinct in various physiological properties compared

with their planktonic and sessile counterparts. “
“A β-galactosidase assay for detecting the accumulation PLX-4720 of NO in the Escherichia coli cytoplasm has been developed based on the sensitive response of the transcription repressor, NsrR, to NO. The hcp promoter is repressed by NsrR in the absence of nitric oxide, but repression is relieved when NO accumulates in the cytoplasm. Most, but not all, of this NO is formed by the interaction of the membrane-associated nitrate reductase, NarG, with nitrite.

External NO at physiologically relevant concentrations does not equilibrate across the E. coli membrane with NsrR in the cytoplasm. The periplasmic nitrite reductase, NrfAB, is not required to prevent equilibration of NO across the membrane. External NO supplied at the highest concentration reported to occur in vivo does not damage FNR sufficiently to affect transcription from the hcp or hmp promoters or from a synthetic promoter. We suggest that the capacity of E. coli to reduce NO is sufficient to prevent its accumulation from external Immune system sources in the cytoplasm. The damaging effects of nitric oxide on proteins, lipids and DNA are well established. Bacteria are exposed to reactive nitrogen species generated from nitrate or nitrite in their environment, generated externally from arginine as a part of the nitrosative burst of mammalian host defence mechanisms, or as products of nitrate, nitrite or ammonia metabolism by bacteria that share their immediate environment. Enteric bacteria have developed multiple mechanisms for protecting themselves from reactive nitrogen species, such as nitric oxide.