Summary: The bidirectional NiFe‐hydrogenase of Synechocystis sp. PCC 6803 is encoded by five genes (hoxEFUYH) which are transcribed as one unit. The transcription of the hox‐operon is regulated by a promoter situated upstream of hoxE. The transcription start point was located at −168 by 5′Race. Several promoter probe vectors carrying different promoter fragments revealed two regions to be essential for the promoter activity. One is situated in the untranslated 5′leader region and the other is found −569 to −690 nucleotides upstream of the ATG. The region further upstream was shown to bind a protein. Even though an imperfect NtcA binding site was identified, NtcA did not bind to this region. The protein binding to the DNA was purified and found to be LexA by MALDI‐TOF. The complete LexA and its DNA binding domain were overexpressed in Escherichia coli. Both were able to bind to two sites in the examined region in band‐shift‐assays. Accordingly, the hydrogenase activity of a LexA‐depleted mutant was reduced. This is the first report on LexA acting not as a repressor but as a transcriptional activator. Furthermore, LexA is the first transcription factor identified so far for the expression of bidirectional hydrogenases in cyanobacteria.

The emergence of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) makes the treatment and control of tuberculosis difficult. Rapid detection of drug-resistant strains is important for the successful treatment of drug-resistant tuberculosis; however, not all resistance mechanisms to the injectable second-line drugs such as amikacin (AK), kanamycin (KM), and capreomycin (CAP) are well understood. This study aims to validate the mechanisms associated with AK, KM, and CAP resistance in M. tuberculosis clinical strains isolated in Thailand.

Since rifampicin resistance is a surrogate marker for multidrug-resistant Mycobacterium tuberculosis (MDRTB), the present study aimed to investigate rpoB mutations conferring rifampicin resistance in M. tuberculosis strains from Thailand, and to develop a rapid, inexpensive and simple PCR-based method for rapid detection of MDRTB. Overall, 267 M. tuberculosis isolates, including 143 MDRTB isolates, were investigated. Isolates of the Beijing strain predominated among the MDRTB isolates (79.1%), but accounted for only 45.5% of the susceptible isolates. Mutations in the rpoB gene were found most commonly at codons 531, 526 and 516 (58%, 25.2% and 9.1%, respectively). A multiplex allele-specific PCR was developed and tested with 216 clinical isolates. In comparison with the proportion method, the method showed 94.2% sensitivity and 100% specificity, and had a 100% positive predictive value and a 95% negative predictive value, which suggested that this method could be useful for screening for MDRTB, particularly in resource-limited countries.