Michael Schweizer

An efficient transformation system has been developed for Neurospora crassa that uses spheroplasts and pVK88 plasmid DNA. pVK88 is a recombinant Escherichia coli plasmid carrying the N. crassa qa-2(+) gene which encodes catabolic dehydroquinase (3-dehydroquinate hydro-lyase, EC 4.2.1.10) and is part of the qa gene cluster. The recipient strain carries a stable qa-2(-) mutation and an arom-9(-) mutation, thus lacking both catabolic and biosynthetic dehydroquinase activities. Transformants were selected as colonies able to grow in the absence of an aromatic amino acid supplement. These colonies were qa-2(+) and had normal levels of catabolic dehydroquinase. DNA.DNA hybridization evidence with appropriate labeled probes indicates clearly that in some instances transformation involves the integration of bacterial plasmid sequences together with the qa-2(+) gene into the N. crassa genome. On the basis of genetic, enzyme assay, and DNA hybridization data, at least three types of transformation events can be distinguished: (i) replacement of the qa-2(-) gene by the qa-2(+) gene without any effect on the expression of the other genes in the qa cluster, (ii) linked insertion of a normal qa-2(+) gene accompanied by inactivation of the adjacent qa-4(+) gene, and (iii) insertion of a normal qa-2(+) gene at an unlinked site in the N. crassa genome. This newly integrated qa-2(+) genetic material is inherited in a typical Mendelian fashion. A low level of transformation has also been obtained by using linear total N. crassa DNA. Two such qa-2(+) transformants are unlinked to the qa-2(-) gene of the recipient.

Acetylenic bonds are present in more than 600 naturally occurring compounds. Plant enzymes that catalyze the formation of the Delta12 acetylenic bond in 9-octadecen-12-ynoic acid and the Delta12 epoxy group in 12,13-epoxy-9-octadecenoic acid were characterized, and two genes, similar in sequence, were cloned. When these complementary DNAs were expressed in Arabidopsis thaliana, the content of acetylenic or epoxidated fatty acids in the seeds increased from 0 to 25 or 15 percent, respectively. Both enzymes have characteristics similar to the membrane proteins containing non-heme iron that have histidine-rich motifs.

As a result of the continuous evolution of microbial pathogens towards antibiotic-resistance, there have been demands for the development of new and effective antimicrobial compounds. Since the 1960s, the scientific literature has accumulated many publications about novel pharmaceutical compounds produced by a diverse range of marine bacteria. Indeed, marine micro-organisms continue to be a productive and successful focus for natural products research, with many newly isolated compounds possessing potentially valuable pharmacological activities. In this regard, the marine environment will undoubtedly prove to be an increasingly important source of novel antimicrobial metabolites, and selective or targeted approaches are already enabling the recovery of a significant number of antibiotic-producing micro-organisms. The aim of this review is to consider advances made in the discovery of new secondary metabolites derived from marine bacteria, and in particular those effective against the so called "superbugs", including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin resistant enterococci (VRE), which are largely responsible for the increase in numbers of hospital acquired, i.e., nosocomial, infections.