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The capabilities of three actinomycetes were examined to solubilize lignocellulose. The three strains were Actinomadura sp., Thermomonospora mesophila and Streptomyces cyaneus. The S. cyaneus revealed the best growth factors among the three species studied, and it also induced lignocellulose solubilization activity faster than the other two. Streptomyces cyaneus also produced a large quantity of extracellular xylanases when fed on ball-milled straw and xylan.

Spiramycin resistance in antibiotic-producing Streptomyces ambofaciens was studied. Analysis of the development of spiramycin resistance revealed at least two distinct mechanisms. A spiramycin-inducible mechanism involving ribosomal modification conferred resistance to spiramycin and other macrolide antibiotics. The second resistance mechanism, observed in non-producing mutants, might be temporally regulated and could involve decreased permeability to the antibiotic.

The adaptation to H2O2 stress in Streptomyces coelicolor was examined. The results show similar adaptations in early-exponential and mid-exponential growth phases following treatment with 20 millimole of H2O2. Adaptation is accompanied by induction of several enzyme activities involved in defense against oxidative stress. Moreover, H2O2-resistant mutants that overexpress several enzyme activities were isolated. Evidence is presented that there is a global regulation of the oxidative response in S. coelicolor.

Analyses of the extracellular proteinases activities of Streptomyces lividans, showed that the major extracellular proteinase produced by this organism is leucine aminopeptidase (LAP). Contrary to previous reports, no significant serine proteinase activity was detected. Further characterization of the S. lividans LAP showed that it requires calcium ions for stability and is most active at 46 degrees celsius and at pH 8.0. The results also showed that the S. lividans LAP is a metallo-enzyme with highly specific substrate preferences produced during the stationary phase of growth.

A gene coding for a non-haem bromperoxidase, termed bpoA2, was isolated from a gene library of Streptomyces aureofaciens ATCC 10762. Sequence analyses showed that bpoA2 codes for a 834 bp open reading frame with 90% identity to BPO-T of S. aureofaciens Tu24. The bpo-A2 gene was cloned in pOP2654 and expressed in S. lividans, leading to a recovery rate of 2 milligrams of homogeneous enzyme per gram of wet cells. The recovered enzyme is very heat-stable, and gives crystals suitable for x-ray diffraction analysis. This expression system will allow for further analyses of the properties of this enzyme.

The regulation of tyrosinase, needed in the formation of melanin, was examined by (super 35)S-labelling experiments and Western blot analysis. Methionine and its analogs induced the de novo formation of tyrosinase, one of the products of the melanin locus in Streptomyces antibioticus. Copper was also required for the synthesis of the active enzyme, although the apoenzyme could be synthesized in the absence of copper. The second component of the melanin locus, ORF 438, was implicated in the extracellular transport of tyrosinase, as well as in the transfer of copper to the apoenzyme.

Thymidine-5'-diphosphate glucose 4,6-dehydratase (TDPGDH) was purified from Streptomyces sp. C5 and S. peucetius ATCC 29050 and was further characterized. The C5 TDPGDH was shown to have monomeric subunits of 39 KDa forming a homodimer, while the S. peucetius had subunits of 36 KDa also forming a homodimer. Both enzymes had a specific requirement for TDP-glucose and nicotinamide adenine dinucleotide, while being inhibited by the thymidine nucleotides. TDP-D-4-keto-6-deoxyglucose was the immediate product formed by both enzymes, toward the biosynthesis of the anthracycline daunorubicin.