|
|
|
|
|
|
Transcriptome and Proteome Analysis of Bacillus subtilis Gene Expression Modulated by Amino Acid Availability. Ulrike Mäder, 2002.A comprehensive study of Bacillus subtilis gene expression patterns in response to amino acid availability was performed by means of proteomics and transcriptomics . The methods of two-dimensional protein gel electrophoresis and DNA macroarray technology were combined to analyze cells exponentially grown in minimal medium with and without 0.2% Casamino Acids (CAA) . This approach revealed about 120 genes predominantly involved in amino acid biosynthesis, sporulation, and competence, which were downregulated in CAA-containing medium . Determination of sporulation frequencies confirmed the physiological relevance of the expression data . Quorum Sensing in Rhizobium sp . Strain NGR234 Regulates Conjugal Transfer (tra) Gene Expression and Influences Growth Rate. Xuesong He, 2003.Rhizobium sp . strain NGR234 forms symbiotic, nitrogen-fixing nodules on a wide range of legumes via functions largely encoded by the plasmid pNGR234a . The pNGR234a sequence revealed a region encoding plasmid replication (rep) and conjugal transfer (tra) functions similar to those encoded by the rep and tra genes from the tumor-inducing (Ti) plasmids of Agrobacterium tumefaciens, including homologues of the Ti plasmid quorum-sensing regulators TraI, TraR, and TraM . In A . tumefaciens, TraI, a LuxI-type protein, catalyzes synthesis of the acylated homoserine lactone (acyl-HSL) N-3-oxo-octanoyl-L-homoserine lactone (3-oxo-C8-HSL) . TraR binds 3-oxo-C8-HSL and activates expression of Ti plasmid tra and rep genes, increasing conjugation and copy number at high population densities . TraM prevents this activation under noninducing conditions . Although the pNGR234a TraR, TraI, and TraM appear to function similarly to their A . tumefaciens counterparts, the TraR and TraM orthologues are not cross-functional, and the quorum-sensing systems have differences . NGR234 TraI synthesizes an acyl-HSL likely to be 3-oxo-C8-HSL, but traI mutants and a pNGR234a-cured derivative produce low levels of a similar acyl-HSL and another, more hydrophobic signal molecule . TraR activates expression of several pNGR234a tra operons in response to 3-oxo-C8-HSL and is inhibited by TraM . However, one of the pNGR234a tra operons is not activated by TraR, and conjugal efficiency is not affected by TraR and 3-oxo-C8-HSL . The growth rate of NGR234 is significantly decreased by TraR and 3-oxo-C8-HSL through functions encoded elsewhere in the NGR234 genome . Use of Phospholipid Fatty Acids To Detect Previous Self-Heating Events in Stored Peat. Sissel Brit Ranneklev, 2003.The use of the phospholipid fatty acid (PLFA) composition of microorganisms to detect previous self-heating events was studied in naturally self-heated peat and in peat incubated under temperature-controlled conditions . An increased content of total PLFAs was found in self-heated peat compared to that in unheated peat . Two PLFAs, denoted T1 and T2, were detected only in the self-heated peat . Incubation of peat samples at 25 to 55°C for 4 days indicated that T1 and T2 were produced from microorganisms with different optimum temperatures . This was confirmed by isolation of bacteria at 55°C, which produced T2 but not T1 . These bacteria produced another PLFA (denoted T3) which coeluted with 18:1  7 . T2 and T3 were identified as
-cyclohexyltridecanoic acid and
-cyclohexylundecanoic acid, respectively, indicating that the bacteria belonged to the genus Alicyclobacillus . T1 was tentatively identified as
-cycloheptylundecanoic acid . T2 was detected 8 h after the peat incubation temperature was increased to 55°C, and maximum levels were found within 5 days of incubation . The PLFA 18:17-T3 increased in proportion to T2 . T1 was detected after 96 h at 55°C, and its level increased throughout the incubation period, so that it eventually became one of the dominant PLFAs after 80 days . In peat samples incubated at 55°C and then at 25°C, T1 and T2 disappeared slowly . After 3 months, detectable levels were still found . Incubation at 25°C after heating for 3 days at 55°C decreased the amounts of T2 and 18:17-T3 faster than did incubation at 5°C . Thus, not only the duration and temperature during the heating event but also the storage temperature following heating are important for the detection of PLFAs indicating previous self-heating .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
