CspB and CspC are induced upon cold shock in Bacillus cereus strain D2

Bacillus cereus D2, a psychrotrophic strain, plays an essential role in the restoration of heavy metal-contaminated soils, especially at low temperatures. However, the cold shock response mechanisms of this strain are unclear. In this study, the cold shock response of B. cereus D2 was characterized; as per the Arrhenius curve, 10 °C was chosen as the cold shock temperature. Six cold shock-like proteins were found and temporarily named cold shock protein (Csp)1-6; the respective genes were cloned and identified. Quantitative real-time PCR results showed that csp1, csp2, csp3, and csp6 were overexpressed under cold shock conditions. Interestingly, after cloning the respective encoding genes into pET-28a (+) vector and their subsequent transformation into E. coli BL21 (DE3), the strains expressing Csp2 and Csp6 grew faster at 10 °C, showing a large number of bacteria. These results suggest that Csp2 and Csp6 are the major cold shock proteins in B. cereus D2. Of note, the comparison of amino acid sequences and structures showed that Csp2 and Csp6 belong to the CspB and CspC families, respectively. Additionally, we show that the number of hydrophobic residues is not a determining feature of major Csps, while, on the other hand, the formation of an α-helix in the context of a leucine residue is the most dominant difference between major, and other Bacillus and E. coli Csps.

SprI/SprR Quorum Sensing System of Serratia proteamaculans 94

In this study, we investigated the quorum sensing (QS) regulatory system of the psychrotrophic strain Serratia proteamaculans 94 isolated from spoiled refrigerated meat. The strain produced several N-acyl-L-homoserine-lactone (AHL) QS signal molecules, with N-(3-oxo-hexanoyl)-L-homoserine lactone and N-(3-hydroxy-hexanoyl)-L-homoserine lactone as two main types. The sprI and sprR genes encoding an AHL synthase and a receptor regulatory protein, respectively, were cloned and sequenced. Analysis of their nucleotide sequence showed that these genes were transcribed convergently and that their reading frames partly overlapped by 23 bp in the terminal regions. The genes were highly similar to the luxI/luxR-type QS genes of other Gram-negative bacteria. An spr-box (analog of the lux-box) was identified upstream of the sprR gene and found to be overlapped with the sequence of −10 sequence site in the promoter region of this gene. Inactivation of the sprI gene led to the absence of AHL synthesis, chitinolytic activity, and swimming motility; decrease of extracellular proteolytic activity; affected the cellular fatty acid composition; and reduced suppression of the fungal plant pathogen mycelium growth by volatile compounds emitted by strain S. proteamaculans 94. The data obtained demonstrated the important role of the QS system in the regulation of cellular processes in S. proteamaculans 94.

Genome Sequence of Oenococcus oeni UNQOe19, the First Fully Assembled Genome Sequence of a Patagonian Psychrotrophic Oenological Strain

Oenococcus oeni UNQOe19 is a native strain isolated from a Patagonian pinot noir wine undergoing spontaneous malolactic fermentation. Here, we present the 1.83-Mb genome sequence of O. oeni UNQOe19, the first fully assembled genome sequence of a psychrotrophic strain from an Argentinean wine.

Removal of Nitrate in Simulated Water at Low Temperature by a Novel Psychrotrophic and Aerobic Bacterium, Pseudomonas taiwanensis Strain J

Low temperatures and high pH generally inhibit the biodenitrification. Thus, it is important to explore the psychrotrophic and alkali-resisting microorganism for degradation of nitrogen. This research was mainly focused on the identification of a psychrotrophic strain and preliminary explored its denitrification characteristics. The new strain J was isolated using the bromothymol blue solid medium and identified as Pseudomonas taiwanensis on the basis of morphology and phospholipid fatty acid as well as 16S rRNA gene sequence analyses, which is further testified to work efficiently for removing nitrate from wastewater at low temperature circumstances. This is the first report that Pseudomonas taiwanensis possessed excellent tolerance to low temperature, with 15°C as its optimum and 5°C as viable. The Pseudomonas taiwanensis showed unusual ability of aerobic denitrification with the nitrate removal efficiencies of 100% at 15°C and 51.61% at 5°C. Single factor experiments showed that the optimal conditions for denitrification were glucose as carbon source, 15°C, shaking speed 150 r/min, C/N 15, pH≥7, and incubation quantity 2.0 × 106 CFU/mL. The nitrate and total nitrogen removal efficiencies were up to 100% and 93.79% at 15°C when glucose is served as carbon source. These results suggested that strain J had aerobic denitrification ability, as well as the notable ability to tolerate the low temperature and high pH.

α-Glucosidase and β-glucosidase from psychrotrophic strain arthrobacter sp. C2-2

In this work six psychophilic and psychrotrophic bacterial strains were screened for the presence of different glycosidase activities (α-galactosidase, α-glucosidase, β-glucosidase, α-mannosidase and β-glucuronidase). Nine enzymes were found and their elementary characteristics were measured (t_optimum, pH_optimum, K_m, V_lim).Two enzymes with the highest activities at low temperatures were chosen for the next study, i.e. α-glucosidase and β-glucosidase from the psychrotrophic strain Arthrobacter sp. C2-2. These enzymes were purified by ammonium sulphate precipitation, by chromatography with hydrophobic interaction, and by ion-exchange chromatography. Their molecular weights (α-glucosidase – 76 kDa, β-glucosidase – 93 kDa) were determined by gel chromatography. In addition to this, it was verified that both of these enzymes are able to catalyse the transglycosylation reaction with the saccharidic donor and acceptor.

A psychrotrophic Burkholderia cepacia strain isolated from refrigerated raw milk showing proteolytic activity and adhesion to stainless steel

The proteolytic activity of a psychrotrophic strain of Burkholderia cepacia isolated from refrigerated raw milk was characterized. Bur. cepacia produced proteolytic activity during growth at refrigeration temperature, with maximum activity at pH 6–7. The enzyme showed relative thermal stability in the range 40–50°C during 25 min, and maintained 80% its initial activity at 76°C/30 s. Milk coagulation assay showed that the crude protease from Bur. cepacia caused coagulation from day 2 for skimmed milk, whereas coagulation was observed from day 5 for whole milk. The adherence of this strain to stainless steel was evaluated, and the substrata had around 107 CFU/cm2 after 15 to 60 min incubation. Results on biofilm development suggest that this bacterium could adhere and to form biofilms even at refrigeration temperatures. These results indicate that Bur. cepacia may represent a potential hazardous to milk and dairy products.

Comparative study of 7 fluorescent pseudomonad clinical isolates

There is some debate about the potential survival of Pseudomonas fluorescens at temperatures above 37 °C and its consequences for infectious potential, owing to the heterogeneity of clinical strains. Seven clinical strains growing at 37 °C or more were submitted for polyphasic identification; 2 were identified as Pseudomonas mosselii and 4 were precisely characterized as P. fluorescens bv. I or II. The binding indexes on glial cells of the strains identified as P. fluorescens bv. I and P. mosselii were compared with that of a reference psychrotrophic strain, P. fluorescens MF37 (bv. V). Clinical P. fluorescens had a similar adherence potential range than strain MF37. Conversely, the binding indexes for P. mosselii strains were 3 times greater than that for strain MF37. These data, and those obtained by comparing the cytotoxic activities of P. fluorescens clinical strains, suggest the existence of different virulence mechanisms, leading either to a low infectious form or to a microorganism with cytotoxic activity in the same range as that of P. mosselii or even Pseudomonas aeruginosa .

Pore Size Dependence on Growth Temperature Is a Common Characteristic of the Major Outer Membrane Protein OprF in Psychrotrophic and Mesophilic Pseudomonas Species

ABSTRACT Pseudomonas species adapt well to hostile environments, which are often subjected to rapid variations. In these bacteria, the outer membrane plays an important role in the sensing of environmental conditions such as temperature. In previous studies, it has been shown that in the psychrotrophic strain P. fluorescens MF0, the major porin OprF changes its channel size according to the growth conditions and could affect outer membrane permeability. Studies of the channel-forming properties of OprFs from P. putida 01G3 and P. aeruginosa PAO1 in planar lipid bilayers generated similar results. The presence of a cysteine- or proline-rich cluster in the central linker region is not essential for channel size modulations. These findings suggest that OprF could adopt two alternative conformations in the outer membrane and that folding is thermoregulated. In contrast, no difference according to growth temperature was observed for structurally different outer membrane proteins, such as OprE3 from the Pseudomonas OprD family of specific porins. Our results are consistent with the fact that the decrease in channel size observed at low growth temperature is a particular feature of the OprF porin in various psychrotrophic and mesophilic Pseudomonas species isolated from diverse ecological niches. The ability to reduce outer membrane permeability at low growth temperature could provide these bacteria with adaptive advantages.