Search

The study of mycobacterial genetics has experienced quick technical developments in the past ten years, despite a relatively slow start, caused by difficulties in accessing these recalcitrant species. The study of mycobacterial pathogenesis is important in the development of new ways of treating tuberculosis and leprosy, now that the emergence of antibiotic-resistant strains has reduced the effectiveness of current therapies. The tuberculosis vaccine strain M. bovis BCG might be used as a vector for multivalent vaccination. Also, non-pathogenic mycobacterial strains have many possible biotechnological applications. After giving a historical overview of methods and techniques, we will discuss recent developments in the search for alternative host strains and DNA transfer systems. Special attention will be given to the development of vectors and techniques for stabilizing foreign DNA in mycobacteria.

Xanthobacter 124X when grom on 4-hydroxyphenylacetate was able to hydroxylate this compound yielding homogenisate. Ring fission of this latter compound gave maleylacetoacetate which was isomerized to fumarylacetoacetate. The isomerase involved resembled maleylacetoacetate isomerases in Gram-negative bacteria in that glutathione was required for activity. Fumarate and acetoacetate were both detected as products of the hydrolysis of fumarylacetoacetate.

The ethylene-oxidizing strain E20 was grown on different carbon sources to obtain information on the metabolism of ethylene from simultaneous adaptation studies and from measurements of specific activities of enzymes in cell-free extracts. From the simultaneous adaptation studies it was concluded that ethylene oxide is a product of ethylene catabolism. The bacterium was also able to grow on the epoxide. From a comparison of the specific activities of isocitrate lyase and malate synthetase in different extracts it was concluded that the glyoxylate cycle was involved in the metabolism of ethylene, indicating that acetyl-CoA is a metabolite of ethylene catabolism. The sequence of reactions leading from ethylene oxide to acetyl-CoA could not be established from the simultaneous adaptation experiments and the enzyme activities in extracts.

A single strain representing the fusiform group of caulobacters first described by Henrici and Johnson has been isolated from a freshwater pond. Like the genusCaulobacter this is a chemo-organotrophic bacterium that has one polar prostheca, a stalk in the sense that its apical holdfast permits the cell to attach to solid substrates. Fine structure studies reveal, however, that the prostheca of this organism contains typical cellular constituents, not the membranous material found in the stalks ofCaulobacter andAsticcacaulis. The organism also differs from the other caulobacters in having no motile stage and no dimorphic life cycle (both daughter cells are stalked at the time of division). Because only one strain has been isolated no nomenclatural proposals are made, but sufficient evidence is presented to indicate that this is a representative of a new genus of the Schizomycetes.