title: Survival of Bacillus spp. SUBB01 at high temperatures and a preliminary assessment of its ability to protect heat-stressed Escherichia coli cells.
abstract: BACKGROUND
  The bacterial stressed state upon temperature raise has widely been observed especially in Escherichia coli cells. The current study extended such physiological investigation on Bacillus spp. SUBB01 under aeration at 100 rpm on different culture media along with the high temperature exposure at 48, 50, 52, 53 and 54 °C. Bacterial growth was determined through the enumeration of the viable and culturable cells; i.e., cells capable of producing the colony forming units on Luria-Bertani and nutrient agar plates up to 24 h. Microscopic experiments were conducted to scrutinize the successive physiological changes. Suppression of bacterial growth due to the elevated heat was further confirmed by the observation of non-viability through spot tests.
  
  
  RESULTS
  As expected, a quick drop in both cell turbidity and colony forming units (~10(4)) along with spores were observed after 12-24 h of incubation period, when cells were grown at 54 °C in both Luria-Bertani and nutrient broth and agar. The critical temperature (the temperature above which it is no longer possible to survive) of Bacillus spp. SUBB01 was estimated to be 53 °C. Furthermore, a positive impact was observed on the inhibited E. coli SUBE01 growth at 45 and 47 °C, upon the supplementation of the extracellular fractions of Bacillus species into the growing culture.
  
  
  CONCLUSIONS
  Overall the present analysis revealed the conversion of the culturable cells into the viable and nonculturable (VBNC) state as a result of heat shock response in Bacillus spp. SUBB01 and the cellular adaptation at extremely high temperature.
authors.affiliation: Department of Microbiology, Stamford University, 51 Siddeswari Road, Dhaka, 1217, Bangladesh. sakilmunna@gmail.com.
authors.forename: Md
authors.initials: M
authors.lastname: Sakil Munna
authors.affiliation: Department of Microbiology, Stamford University, 51 Siddeswari Road, Dhaka, 1217, Bangladesh. tahera.mbo271@yahoo.com.
authors.forename: Jannatun
authors.initials: J
authors.lastname: Tahera
authors.affiliation: Department of Microbiology, Stamford University, 51 Siddeswari Road, Dhaka, 1217, Bangladesh. auntoafrad@gmail.com.
authors.forename: Md
authors.initials: M
authors.lastname: Mohibul Hassan Afrad
authors.affiliation: Department of Microbiology, Stamford University, 51 Siddeswari Road, Dhaka, 1217, Bangladesh. tun.ifra@yahoo.com.
authors.forename: Ifra Tun
authors.initials: IT
authors.lastname: Nur
authors.affiliation: Department of Microbiology, Stamford University, 51 Siddeswari Road, Dhaka, 1217, Bangladesh. noor.rashed@yahoo.com.
authors.forename: Rashed
authors.initials: R
authors.lastname: Noor
mesh_terms: D001407:Bacillus / Q000166:cytology / Q000254:growth & development / Q000502:physiology*; D018407:Bacterial Physiological Phenomena; D001431:Bacteriological Techniques / Q000379:methods; D003593:Cytoplasm / Q000502:physiology; D004926:Escherichia coli / Q000254:growth & development / Q000502:physiology*; D018869:Heat-Shock Response / Q000502:physiology; D006358:Hot Temperature; D050296:Microbial Viability; D013997:Time Factors