title: Response of Lactobacillus helveticus PR4 to heat stress during propagation in cheese whey with a gradient of decreasing temperatures.
abstract: The heat stress response was studied in Lactobacillus helveticus PR4 during propagation in cheese whey with a gradient of naturally decreasing temperature (55 to 20 degrees C). Growth under a gradient of decreasing temperature was compared to growth at a constant temperature of 42 degrees C. Proteinase, peptidase, and acidification activities of L. helveticus PR4 were found to be higher in cells harvested when 40 degrees C was reached by a gradient of decreasing temperature than in cells grown at constant temperature of 42 degrees C. When cells grown under a temperature gradient were harvested after an initial exposure of 35 min to 55 degrees C followed by decreases in temperature to 40 (3 h), 30 (5 h 30 min), or 20 degrees C (13 h 30 min) and were then compared with cells grown for the same time at a constant temperature of 42 degrees C, a frequently transient induction of the levels of expression of 48 proteins was found by two-dimensional electrophoresis analysis. Expression of most of these proteins increased following cooling from 55 to 40 degrees C (3 h). Sixteen of these proteins were subjected to N-terminal and matrix-assisted laser desorption ionization-time of flight mass spectrometry analyses. They were identified as stress proteins (e.g., DnaK and GroEL), glycolysis-related machinery (e.g., enolase and glyceraldehyde-3-phosphate dehydrogenase), and other regulatory proteins or factors (e.g., DNA-binding protein II and ATP-dependent protease). Most of these proteins have been found to play a role in the mechanisms of heat stress adaptation in other bacteria.
authors.affiliation: Dipartimento di Protezione delle Piante e Microbiologia Applicata, Facoltà di Scienze Biotecnologiche di Bari, Via G. Amendola 165/a, 70126 Bari, Italy.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Di Cagno
authors.forename: Maria
authors.initials: M
authors.lastname: De Angelis
authors.forename: Antonio
authors.initials: A
authors.lastname: Limitone
authors.forename: Patrick F
authors.initials: PF
authors.lastname: Fox
authors.forename: Marco
authors.initials: M
authors.lastname: Gobbetti
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002611:Cheese / Q000382:microbiology*; D015180:Electrophoresis, Gel, Two-Dimensional; D015964:Gene Expression Regulation, Bacterial; D018869:Heat-Shock Response; D006358:Hot Temperature; D007700:Kinetics; D052198:Lactobacillus helveticus / Q000254:growth & development* / Q000378:metabolism; D008969:Molecular Sequence Data; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013696:Temperature
chemical_list: D001426:Bacterial Proteins