Biomedical subjects

Richard Robison

Publications and source records attributed to Richard Robison.

4 recordsLinked to original sources

PubMed2006

Munumbicins E-4 and E-5: novel broad-spectrum antibiotics from Streptomyces NRRL 3052.

Streptomyces NRRL 30562 was originally isolated as an endophyte from Kennedia nigriscans, snakevine, in the Northern Territory of Australia. This plant has been used for centuries by Aboriginal peoples to treat open bleeding wounds to prevent sepsis. A solvent extract of the crude fluid from cultures of this endophyte possesses wide-spectrum antibiotic activity. Some of the bioactivity is associated with the appearance of actinomycins X2, D, and Xobeta, the first two of which had been previously designated munumbicins A and B, respectively. Other novel compounds bearing wide-spectrum antibiotic activity are also produced by Streptomyces NRRL 30562, and these are designated munumbicins E-4 and E-5. Mass spectrometric analyses of these peptide antibiotics show that they have identical masses (1445.00) but different retention times on HPLC. Both compounds showed activity against gram-positive and gram-negative bacteria. The plant pathogenic fungus, Pythium ultimum is sensitive to both munumbicins at 5.0 microg mL(-1) The malarial parasite, Plasmodium falciparum has IC50 values of 0.50+/-0.08 and 0.87+/-0.0.26 microg mL(-1) for E-4 and E-5, respectively. It appears that other bioactive compounds, related to E-4 and E-5, are also produced making it the most biologically active endophytic Streptomyces spp. on record.

Animals↗

PubMed2006

Diagnostic oligonucleotide microarray fingerprinting of Bacillus isolates.

A genome-independent microarray and new statistical techniques were used to genotype Bacillus strains and quantitatively compare DNA fingerprints with the known taxonomy of the genus. A synthetic DNA standard was used to understand process level variability and lead to recommended standard operating procedures for microbial forensics and clinical diagnostics.

Bacillus↗

PubMed2003

Kakadumycins, novel antibiotics from Streptomyces sp NRRL 30566, an endophyte of Grevillea pteridifolia.

An endophytic streptomycete (NRRL 30566) is described and partially characterized from a fern-leaved grevillea (Grevillea pteridifolia) tree growing in the Northern Territory of Australia. This endophytic streptomycete produces, in culture, novel antibiotics - the kakadumycins. Methods are outlined for the production and chemical characterization of kakadumycin A and related compounds. This antibiotic is structurally related to a quinoxaline antibiotic, echinomycin. Each contains, by virtue of their amino acid compositions, alanine, serine and an unknown amino acid. Other biological, spectral and chromatographic differences between these two compounds occur and are given. Kakadumycin A has wide spectrum antibiotic activity, especially against Gram-positive bacteria, and it generally displays better bioactivity than echinomycin. For instance, against Bacillus anthracis strains, kakadumycin A has minimum inhibitory concentrations of 0.2-0.3 microg x ml(-1) in contrast to echinomycin at 1.0-1.2 microg x ml(-1). Both echinomycin and kakadumycin A have impressive activity against the malarial parasite Plasmodium falciparum with LD(50)s in the range of 7-10 ng x ml(-1). In macromolecular synthesis assays both kakadumycin A and echinomycin have similar effects on the inhibition of RNA synthesis. It appears that the endophytic Streptomyces sp. offer some promise for the discovery of novel antibiotics with pharmacological potential.

Anti-Bacterial Agents↗

PubMed2002

Munumbicins, wide-spectrum antibiotics produced by Streptomyces NRRL 30562, endophytic on Kennedia nigriscans.

Munumbicins A, B, C and D are newly described antibiotics with a wide spectrum of activity against many human as well as plant pathogenic fungi and bacteria, and a Plasmodium sp. These compounds were obtained from Streptomyces NRRL 3052, which is endophytic in the medicinal plant snakevine (Kennedia nigriscans), native to the Northern Territory of Australia. This endophyte was cultured, the broth was extracted with an organic solvent and the contents of the residue were purified by bioassay-guided HPLC. The major components were four functionalized peptides with masses of 1269.6, 1298.5, 1312.5 and 1326.5 Da. Numerous other related compounds possessing bioactivity, with differing masses, were also present in the culture broth extract in lower quantities. With few exceptions, the peptide portion of each component contained only the common amino acids threonine, aspartic acid (or asparagine), glutamic acid (or glutamine), valine and proline, in varying ratios. The munumbicins possessed widely differing biological activities depending upon the target organism. For instance, munumbicin B had an MIC of 2.5 microg x ml(-1) against a methicillin-resistant strain of Staphylococcus aureus, whereas munumbicin A was not active against this organism. In general, the munumbicins demonstrated activity against Gram-positive bacteria such as Bacillus anthracis and multidrug-resistant Mycobacterium tuberculosis. However, the most impressive biological activity of any of the munumbicins was that of munumbicin D against the malarial parasite Plasmodium falciparum, having an IC(50) of 4.5+/-0.07 ng x ml(-1). This report also describes the potential of the munumbicins in medicine and agriculture.

Amino Acids↗