Aims: To study the relationship between changes in the composition of the outer membrane proteins and the survival of Salmonella typhimurium LT2 in filtered autoclaved seawater containing Toluidine Blue (TB) dye as a photosensitizer. Methods and Results: In samples exposed to TB and excited by artificial visible light, the total viable (TVC) and respiring cell counts (RCC) showed that, although the TVC declined to an undetectable level in 6·5 h, the RCC showed that some cells were still capable of respiration. The porin protein composition changed gradually with OmpC and OmpF becoming undetectable by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis after 8 h of incubation. Hydrogen peroxide‐pretreated cells survived longer compared with the control. Conclusions: Oxidative pretreatment of Salm. typhimurium protects cells from some of the effects of sunlight in the presence of photosensitizers. The changes in porin proteins may play a role in this protection. Significance and Impact of the Study: The study shows that the survival of bacteria under conditions of stress is the result of a linked series of reactions.

In this study, 26 Pseudomonas spp. were isolated from a stream polluted by factory waste and from petroleum-contaminated soil. The surface tension (ST) of the cultures was used as a criterion for the primary isolation of biosurfactant-producing bacteria. Biosurfactant production was quantified by ST reduction, critical micelle concentration (CMC), emulsification capacity (EC), and cell surface hydrophobicity (CSH). Two of the isolates, P. aeruginosa 78 and 99, produced rhamnolipid biosurfactant. The strains started rhamnolipid production in the logarithmic phase. They decreased the ST of the culture from 73 dyne/cm 2 to 29 and 33 dyne/cm 2 , and the CMC of produced rhamnolipids were 115 and 130 mg/L, respectively. P. aeruginosa 78 and 99 strains emulsified benzene and n-hexane at the highest rates, and the surfaces of these strains were 73% and 65% and 62% and 72% more hydrophobic for benzene and toluene, respectively.

The aim of this study was to investigate the impact on numbers of using different media for the enumeration of Escherichia coli subjected to stress, and to evaluate the use of different resuscitation methods on bacterial numbers. E. coli was subjected to heat stress by exposure to 55 degrees C for 1h or to light-induced oxidative stress by exposure to artificial light for up to 8h in the presence of methylene blue. In both cases, the bacterial counts on selective media were below the limits of detection whereas on non-selective media colonies were still produced. After resuscitation in non-selective media, using a multi-well MPN resuscitation method or resuscitation on membrane filters, the bacterial counts on selective media matched those on non-selective media. Heat and light stress can affect the ability of E. coli to grow on selective media essential for the enumeration as indicator bacteria. A resuscitation method is essential for the recovery of these stressed bacteria in order to avoid underestimation of indicator bacteria numbers in water. There was no difference in resuscitation efficiency using the membrane filter and multi-well MPN methods. This study emphasises the need to use a resuscitation method if the numbers of indicator bacteria in water samples are not to be underestimated. False-negative results in the analysis of drinking water or natural bathing waters could have profound health effects.

In this study, the effect of the incubation time, incubation temperature, pH, metal and sodium ions on the antibacterial activity of chitosan against food borne spoilage bacteria focused. Aeromonas hydrophila and Staphylococcus aureus were used as two food borne bacteria. Acetic acid was used dissolving of chitosan. Results showed that chitosan solution at 5 mg/mL significantly inhibited the growth of A. hydrophila and S. aureus in presence of time, pH and metal ions (p <0.01). However, temperature did not significantly affect the antibacterial activity (4°C, 25°C and 37°C) (p >0.01). Chitosan activity increased with increasing incubation time. The influence of below pH 6 on the antibacterial activity of chitosan was significantly influenced (p<0.01). The addition of Ba+2 reduced chitosan activity against A. hydrophila while the addition of Ca+2 have increased chitosan activity against S. aureus. Sodium ions at a concentration of 25 mM reduced chitosan activity against S. aureus. These results show that chitosan can be used food industry to prevent the development of spoilage bacteria. Erdem et al., International Current Pharmaceutical Journal, April 2016, 5(5): 45-48

No abstract