Selective adsorption of Mycobacterium Phlei on pyrite and sphalerite.

The adsorption of Mycobacterium Phlei cells on the surfaces of pyrite and sphalerite was studied as functions of time and pH. The results indicated that a higher amount of cells adsorbing onto pyrite compared with that onto sphalerite under neutral and alkaline conditions, and it was also observed from photographs of scanning electron micrograph. To gain a better insight into the mechanisms of differential adsorption, the functional groups on cell surfaces and the chemical states of each element on mineral surfaces before and after interaction with bacterial cells were investigated. The results showed that many groups presented on cells surface, such as C-O-H, C-O-C, C=O, C-N, N-H and P=O. The change in state of each element on pyrite and sphalerite surfaces after interaction with bacterial cells revealed that there were chemical reactions between metal ions and S on mineral surface and atoms like N, O, P, etc. on cell surface, and the shifts in binding energy of each element on pyrite surface is larger than that of sphalerite. Possible mechanisms for selective adsorption of bacterial cells onto pyrite and sphalerite were discussed in the latter part of this paper.

Phenotypic changes in mycobacteria grown in oxygen-limited conditions.

Laboratory strains of Mycobacterium phlei, M. smegmatis, M. fortuitum, M. gordonae, M. kansasi, M. bovis, M. tuberculosis and M. intracellulare were adapted to grow in an anaerobic environment. Concomitant with the transition to anaerobic growth was loss of acid-fastness, loss or modification of colonial pigmentation, and loss of ability to grow on a malachite green-containing medium. The mycobacteria grown anaerobically produced acid from a greater range of carbohydrates than aerobically grown cultures, lost iron-uptake activity, and showed a reduction of urease, catalase and nitratase activity. Back adaption of mycobacteria from an anaerobic to an aerobic environment resulted in the acquisition of acid-fastness, pigmentation, and other characteristics used in the taxonomy of mycobacteria. These results suggest that mycobacterial cultures, if grown in an anaerobic environment, may be erroneously identified in clinical laboratories.

Cell cycle in Mycobacterium phlei.

The initial replication region of the chromosome on the replication map of M. phlei constructed by means of sequential mutagenesis in synchronous populations was accurately determined. By following the time shift of the replication moment of the genes bac and met in the control culture and in the culture with the initial inhibition of DNA synthesis by nalidixic acid the start of replication of the chromosome was determined at 15 min before replication of the gene ile. On the basis of the results obtained a scheme of the cell cycle in M. phlei was proposed. Intervals C and D depend on the generation time, become prolonged independently of each other and assume the whole cycle. The ratio C/(C + D) equals to 0.56 and the interval D has a value of 0.76 of the interval C. The mutual ratio of the intervals C : D is 1.3 : 1.0. The obtained results make it possible to form the assumption about mutual ratios between the chromosome replication and cell division in bacteria exhibiting slow growth rates.