Identification of marine algicidal Flavobacterium sp. 5 N-3 using multiple probes and whole-cell hybridization

ABSTRACT: We designed five 16S rRNA-targeted oligonucleotide probes (Sp probes) specific for Flavobacterium sp. 5 N-3, which inhibits the growth of red tide phytoplankton Gymnodinium mikimotoi (Dinophyceae). These probes were evaluated by whole-cell hybridization against 5 N-3 cells incubated under laboratory conditions. The fluorescence signal from the cell detected with Sp probe mix5, a mixture of the five probes, was 8.4-fold higher than that obtained with only one Sp probe (Sp01RF). The signal obtained by this method was strong enough to recognize 5 N-3 cells and count them under the epifluorescence microscope, while the signal was often undetectable when a single probe was used. Fluorescence intensities of cells at stationary phases and of 'starved' cells in sterile seawater using Sp probe mix5 were low but still sufficient for enumeration. These Sp probes did not hybridize with 11 strains from the Cytophaga/Flavobacteria/Bacteroides phylum and did react with strain 5 N-3 following whole-cell hybridization. These results show that 5 N-3 cells cultivated under our laboratory conditions can be detected by whole-cell hybridization with the five designed probes. These data also suggest that this technique may be useful for detection of an algicidal bacterium 5 N-3 in the natural environment.     

海洋深层水在日本水产养殖中的应用概况

随着我国经济的飞速发展，人民生活水平的日益提高，人们对各种高档、稀有水产品的需求越来越多，为了满足这种需求，本文系统介绍日本海洋科技工作者利用海洋深层水养殖、培育高档鱼类方面所取得的部分成果，以供我国水产养殖科技工作者借鉴。     

Characterization and distribution of Staphylococcus sp. implicated for improvement of fish sauce odor

ABSTRACT:   The two Staphylococcus strains that had been isolated from fish sauce mush (moromi) made from frigate mackerel in Japan and proved to improve fish sauce odor, were examined for their taxonomic positions. The sequence analysis based on 16S rRNA and rpoB showed that the two strains, R4Nu and R5G, had an identical sequence with sequence identities of 99.5% and 99.0% to the above two genes from the closest species of S. nepalensis , respectively. A DNA hybridization test of the two strains showed more than 80% DNA similarity with S. nepalensis , thus confirming the above-mentioned species identification. Polymerase chain reaction primers specific to the strain isolated from fish sauce mush were designed from rpoB and examined for the distribution of this species to various fish sauces made in Asian countries as well as to fish sauce starter (malt) made from soy beans and barley in Toyama Prefecture, Japan. The amplified DNA fragment bearing the S. nepalensis gene was detected in the enriched culture of the malt, although no positive reaction was shown with fish sauce samples. These results suggest that S. nepalensis indebted to improve fish sauce odor was originated from the fish sauce starter malt.