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In this study, the expression of four reference genes (β-actin, EF1-α, GAPDH, and SubF0), two prophenoloxidase genes (proPO1 and proPO2), and the distribution of phenoloxidase (PO) activity in eight tissues (carapace, cuticle, hemolymph, hepatopancreas, muscle, pereiopods, pleopods, and uropods) of black tiger shrimp (Penaeus monodon) were evaluated. According to the geNorm and NormFinder algorithms, the most stable reference gene or the best combinations of reference genes for the evaluation of proPO1 and proPO2 expression are SubF0 for cuticle, muscle, and uropods, EF1-α for hemolymph and pereiopods, EF1-α + SubF0 for carapace, β-actin + SubF0 for hepatopancreas, and β-actin + GAPDH for pleopods. In the hemolymph and uropods, proPO1 expression was significantly stronger than that of proPO2 (433 and 5 times higher, respectively). However, in hepatopancreas, proPO2 expression was significantly stronger than proPO1 (36 times higher). Trypsin cleaves the proPO zymogen into active PO in most of the studied tissues, except hepatopancreas. PO activity (units/mg protein) following trypsin activation varied among the tissues in the following order: uropods > hemolymph > pleopods > pereiopods > hepatopancreas > carapace > cuticle > muscle. The results indicate that proPO1 is dominant in hemolymph, whereas proPO2 is dominant in hepatopancreas. Altogether, these results contribute to the elucidation of the phenoloxidase function in P. monodon. [ABSTRACT FROM AUTHOR]

The respiratory activities of oral streptococci grown in biofilms were found to be markedly repressed compared with those of cells from aerobic culture, or for Streptococcus mutans GS-5, even for those grown in static culture. Respiration rates generally reflected levels of NADH oxidase activities in cell extracts. Superoxide dismutase levels were somewhat reduced in biofilm cells. However, sensitivities to oxidative damage caused by H2O2, t-butylhydroperoxide, or 8-hydroxyquinoline were not greatly different for cells from suspension cultures and those from either intact or dispersed biofilms. The capacities of S. sanguis and S. gordonii to produce H2O2 also were markedly repressed by biofilm growth, and presumably this repression would affect the ecology of dental plaque by reducing oxidative stresses under crowded conditions. [ABSTRACT FROM AUTHOR]

Fluoride and other weak acids, such as benzoate, indomethacin, salicylate and sorbate, were found to be sensitizers for acid killing of cells of Actinomyces naeslundii ATCC 19246 and Streptococcus sanguis NCTC 10904 in suspensions or in mono-organism biofilms on glass slides. These bacteria are among the more acid-sensitive organisms from dental plaque and were killed when acidified to pH values between 3.5 and 4.0. Biofilm cells were more resistant than cells in suspensions, especially in terms of the fraction of the initial population surviving acidification. The mechanism for sensitization to acid killing by fluoride and the other weak acids involved enhanced transmembrane transport of protons, reflected by increases in measured proton permeabilities of the cells. Thus, the weak acids thwarted the functions of F(H+)-ATPases in extruding protons and protecting cells against acid damage. Fluoride sensitization of biofilms or cells in suspensions to acid damage occurred rapidly. There was a delay in sensitization of biofilms by indomethacin and higher molecular weight acids which was interpreted in terms of diffusion limitation of sensitizer penetration. Overall, it seemed that weak-acid sensitization to acid killing is a general phenomenon that occurs not just for oral bacteria but also for organisms in food, soil, and other acidified environments. [ABSTRACT FROM AUTHOR]