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To improve the efficiency of screening for anti-Microcystis compounds, we planned to use algae-lysing bacteria that kill the organisms of water blooms. A two step-screening process was carried out, i.e., the screening of algae-lysing bacteria and the selection of anti-Microcystis producers from the bacteria. Sources for the isolation of the bacteria were a co-cultivated fluid of a water sample with axenic Microcystis viridis, a water sample collected in a water bloom season, and a water bloom sample. The water bloom sample was the best source for the isolation of the algae-lysing bacteria and such bacteria were shown to exhibit potent activity. Seventeen strains out of 20 isolated algae-lysing bacteria produced anti-Microcystis activities, and one of the principles was the previously reported argimicin A. These results indicate that algae-lysing bacteria in water blooms may be good sources for potent and selective anticyanobacterial compounds.

A novel acaricide, gualamycin was isolated from the culture broth of Streptomyces sp. NK11687. The structure of gualamycin was determined to be (2R,3S,4S)-2-O-[4-O-(2-amino-2-deoxy-beta-D-gulopyranosyl)-alpha-D - galactopyranosyl]-2,3,4-trihydroxy-4-[(2S,3S,4S,5S)-3,4-dihydroxy-5-hydr oxy - methylpyrrolidin-2-yl] butanoic acid by FAB-MS, 1H and 13C NMR, COSY, HMQC, HMBC, IR, X-ray crystallographic analyses and synthetic studies.

A novel acaricide, gualamycin, was isolated from the culture broth of Streptomyces sp. NK11687. It was purified from the filtrate by column chromatographies. Gualamycin showed 100% acaricidal activity at 250 micrograms/ml against sensitive and resistant mites to Dicofol.

A novel plant growth regulator, pironetin, was isolated from the culture broth of Streptomyces sp. NK10958. It was extracted from the culture broth with ethyl acetate and purified by column chromatographies. Pironetin showed 23% inhibition on the growth of rice plants without any loss of crop yield at 10 g/a on 9 days before heading.

A novel plant growth regulator, pironetin was isolated from the culture broth of Streptomyces sp. NK10958. The structure of pironetin was determined to be (5R,6R)-5-ethyl- 5,6-dihydro-6-[(E)-(2R,3S,4R,5S)-2-hydroxy-4-methoxy-3,5-dimethyl-7- nonenyl]-2H-pyran-2-one by FAB-MS, 1H and 13C NMR, COSY, COLOC, DEPT, IR, X-ray crystallographic analyses and adapted Mosher's method.

Oligomycin antibiotics, 44-homooligomycin A (NK86-0279 II) and B (NK86-0279 I) are newly discovered antitumor antibiotics with the substitution of ethyl for methyl at carbon 26. They were isolated from the culture broth of Streptomyces bottropensis NK86-0279. The structure of these two compounds was deduced by spectroscopic and X-ray crystallographic analyses. These antibiotics showed potent antitumor activities against various tumor cells in vitro, and were active against Colon 26 carcinoma in vivo. Although they showed no activity at 1,000 micrograms/ml against Gram-positive and Gram-negative bacteria and yeast, they have antifungal activity.

The antiviral activity of a new guanosine analog, 9-(2-deoxy-2-hydroxymethyl-beta-D-erythrooxetanosyl)guanine (OXT-G), against guinea pig cytomegalovirus (GPCMV) was evaluated both in vitro and in vivo. In the plaque reduction assay, the median effective concentration (EC50) of OXT-G, ganciclovir (DHPG) and acyclovir (ACV) against GPCMV was 0.03, 6.4 and 52 micrograms/ml, respectively. The selectivity index, based on the ratio of the median inhibitory concentration for cell growth of guinea pig embryo fibroblasts to the median effective concentration for GPCMV plaque formation, was about 100-fold higher than that of DHPG. In an in vivo study, Hartley guinea pigs infected with GPCMV were treated with OXT-G or DHPG (20 mg/kg/day) for 2 weeks, and it was found that virus titers in the salivary gland were 70-fold lower in OXT-G-treated guinea pigs than in DHPG-treated animals. The results indicate that OXT-G was more potent and selective against GPCMV infection than DHPG.

Deoxypheganomycin D, a specific inhibitor of mycobacteria, inhibits the growth in vitro of Mycobacterium smegmatis ATCC 607 (M. 607) bacteriostatically at concentrations as high as 7 X 10(-5) M. It shows no cross-resistance to paromomycin, capreomycin, viomycin, streptothricin, kanamycin and streptomycin. Deoxypheganomycin D at 2.8 X 10(-7) M where the cell growth of M. 607 is only partially inhibited does not significantly inhibit DNA, RNA or protein synthesis but leads to marked decrease (13% of control) in [14C]glycerol-derived radioactivity in cell-walls. In the presence of 7 X 10(-6) M deoxypheganomycin D, the influx of leucine but not thymidine is affected while the reverse is true with efflux. The data suggest that the effect of deoxypheganomycin D on M. 607 may be related to both the cell membrane and specific mycobacterial lipid like components of the cell-wall.

Oxanosine, a novel nucleoside, inhibits the growth of Escherichia coli K-12 on peptone agar, but not on Nutrient agar. This antibiotic activity was found to be bacteriostatic and was antagonized by guanine, guanosine, and guanylic acid. The growth of leukemia L 1210 cell was also inhibited by oxanosine, and the inhibition was reversed by guanylic acid. Oxanosine was confirmed to be a competitive inhibitor of GMP synthetase (E.C. 6.3.5.2) and the Ki value was 7.4 X 10(-4) M.