Identification and expression of stressosomal proteins in Mycobacterium marinum under various growth and stress conditions.

Like other bacteria, Mycobacterium spp. have developed different strategies in response to environmental changes such as nutrient limitations and other different stress situations. We have identified candidate genes (rsb genes) from Mycobacterium marinum involved in the regulation of the activity of the alternative sigma factor, σ(F) . This is a homolog of the master regulator of general stress response, σ(B) , and the sporulation-specific sigma factor, σ(F) , in Bacillus subtilis. The organization of these genes in M. marinum and B. subtilis is similar. Transcriptome and qRT-PCR data show that these genes are indeed expressed in M. marinum and that the levels of expression vary with growth phase and exposure to stress. In particular, cold stress caused a significant rise in the expression of all identified rsb and sigF genes. We discuss these data in relation to what is currently known for other Mycobacterium spp.

Growth, cell division and sporulation in mycobacteria.

Bacteria have the ability to adapt to different growth conditions and to survive in various environments. They have also the capacity to enter into dormant states and some bacteria form spores when exposed to stresses such as starvation and oxygen deprivation. Sporulation has been demonstrated in a number of different bacteria but Mycobacterium spp. have been considered to be non-sporulating bacteria. We recently provided evidence that Mycobacterium marinum and likely also Mycobacterium bovis bacillus Calmette-Guérin can form spores. Mycobacterial spores were detected in old cultures and our findings suggest that sporulation might be an adaptation of lifestyle for mycobacteria under stress. Here we will discuss our current understanding of growth, cell division, and sporulation in mycobacteria.

Bicyclic peptides as potent inhibitors of histone deacetylases: optimization of alkyl loop length.

Bicyclic tetrapeptide hydroxamic acids were prepared as histone deacetylase (HDAC) inhibitors, and the evaluated inhibitory activity shows that they are potent against HDAC1 and HDAC4. The in vivo activity depends on alkyl loop length.

Sporulation in mycobacteria.

Mycobacteria owe their success as pathogens to their ability to persist for long periods within host cells in asymptomatic, latent forms before they opportunistically switch to the virulent state. The molecular mechanisms underlying the transition into dormancy and emergence from it are not clear. Here we show that old cultures of Mycobacterium marinum contained spores that, upon exposure to fresh medium, germinated into vegetative cells and reappeared again in stationary phase via endospore formation. They showed many of the usual characteristics of well-known endospores. Homologues of well-known sporulation genes of Bacillus subtilis and Streptomyces coelicolor were detected in mycobacteria genomes, some of which were verified to be transcribed during appropriate life-cycle stages. We also provide data indicating that it is likely that old Mycobacterium bovis bacillus Calmette-Guérin cultures form spores. Together, our data show sporulation as a lifestyle adapted by mycobacteria under stress and tempt us to suggest this as a possible mechanism for dormancy and/or persistent infection. If so, this might lead to new prophylactic strategies.

Simultaneous quantitation of five flavonoid glycosides in Herba Epimedii by high-performance liquid chromatography-tandem mass spectrometry.

A rapid and accurate reversed-phase liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method has been developed and validated for the quantitative determination of five flavonoid glycosides, icariin, epimedin A, epimedin B, epimedin C and hyperin in Herba Epimedii. Chromatographic separations were performed using a C(18) narrow-bore HPLC column; a mixture of an aqueous solution of ammonium formate (pH 4.0) and acetonitrile was used as the mobile phase, with compounds detected in the positive ion mode with multiple-reaction monitoring using a triple-quadrupole mass spectrometer equipped with an electrospray ionisation interface. This method for the determination of the reported flavonoid glycosides was accurate and reproducible, with a lower limit of quantication of 0.5 microg/mL. The standard calibration curves for the above-mentioned compounds were linear (r(2) > 0.998) over the concentration range 0.5-10.0 microg/mL. The relative standard deviations for intra- and inter-day precision over the concentration range for the flavonoid glycosides were lower than 7.8% with accuracy between 90.1 and 111.0%. The established method was successfully applied to the quality assessment of samples of Herba Epimedii collected from Korea and China.