mean??SD for cells are killed and intracellular components released. value of (100\CFR)% at 24?h indicated a lethal effect. When cells were cultivated on TSA comprising 10% sucrose, the time delay was 4?h and the lethal effect was 4%. However, deceased cells inhibited the growth of live cells. Physical contact with insoluble matter derived from deceased cells or deceased cells themselves might have caused growth Rabbit polyclonal to KBTBD7 inhibition. These findings focus on a novel perspective on colony count methods in practical situations, such as when sampling foods comprising a high concentration of sucrose. AbbreviationsCFDA6\carboxyfluorescein diacetateCFRcolony\forming rateFCSforward scatterSSCside scatterTSAtryptic soy agarTSA\Suctryptic soy agar and sucroseTSBtryptic soy broth Food and water products are sterilized to prevent microbial contamination, and its performance is checked by test Zoledronic Acid methods that involve the measurement of the amount of bacterial cells remaining in Zoledronic Acid products. Test methods are based on a colony count using appropriate agar media. Globally validated research methods are wholly based on the colony count method [1, 2]. The formation of a colony with a visible size is evidence that the original solitary bacterial cell was living. It is well recognized that colony formation is affected by various factors, such as medium composition, culture temp, culture time, aerobic or anaerobic conditions, and sample\derived coexisting substances. Occasions happen when that food sample\derived substances might cause false\positive or false\bad results [3, 4]. These factors need to be cautiously regarded as in practical checks. A more hard issue is the living of injured bacteria [5, 6, 7, 8]. Freezing, drying, freeze\drying, heating, \radiation, and osmotic stress are treatments that might cause sublethal effects on bacterial cells. Actually if the degree of injury is definitely small, hurt cells might not necessarily form colonies. Such cells might be regarded as nonculturable hurt cells. When culture conditions are improved, however, such cells might recover from injury and grow to a colony of normal size with time. Such a case may become regarded as a false\bad result. If the injury is serious, hurt cells pass away. Such deceased cells are believed to not affect colony count results. In this study, osmotic stress was selected like a cause of injury from among a variety of stresses. Regarding the effects of deceased cells, several factors released from bacterial cells might remain after their death to influence live bacterial cells. For example, autoinducers released by were reported to be involved in quorum sensing [9, 10] and to suppress the growth of additional bacterial cells. It was also demonstrated that apoptosis\inducing factors were generated by were prepared to investigate the effect of deceased bacterial cells on live bacterial cells. Materials and methods Microorganism ATCC8739, from Zoledronic Acid the American Type Tradition Collection (Manassas, VA, USA), was precultured in tryptic soy broth (TSB; Becton Dickinson Co., Cockeysville, MD, USA); and its cell suspension was plated onto tryptic soy agar (TSA; Becton Dickinson Co., Cockeysville, MD, USA) and cultured at 37?C. Preparation of hurt cells by sorting cells directly onto TSA comprising sucrose Cell sorting was carried out relating to a circulation cytometric method as previously explained [13, 14]. Briefly, live solitary\cells of were live\stained with 6\carboxyfluorescein diacetate (CFDA) (Sigma\Aldrich Japan, Tokyo, Japan). A plate, 86?mm in diameter, containing TSA and sucrose (TSA\Suc plate) was collection on an automatic stage installed inside a cell sorter (FACSAria II; BD Co.). The automatic stage was used so that 100 cells could be sorted into a 10??10 grid pattern of spots at 1 cell/spot. The denseness of sucrose in TSA assorted from 10% to 50%. During tradition at 37?C, the number of colonies was automatically recorded using a Biomatic? S12 (MicroBio Corporation, Sendai, Japan). The threshold Zoledronic Acid size of a colony was modified to 65?m in diameter. The CFR was defined as 100??was the number of colonies. In this study, (%). Isolation of solitary injured cells.