@misc{oai:ir.kagoshima-u.ac.jp:00003826,
 author = {Md. Iftekharul Wahid and Md. イフテカルル ワヒド},
 month = {2016-10-27, 2016-10-27},
 note = {学位論文の要旨, 学位論文本文, Thirteen strains of labyrinthulids were isolated from the coastal area of Kagoshima Bay, Kagoshima Prefecture, Japan and from Batan Bay, Panay Island, the Philippines by using diatom double-layer agar plates. The cells of labyrinthulid isolates grew axenically on the bacterial dead cells and extract plus egg yolk agar medium (NSBEY agar). Three representative isolates were demonstrated to belong to the labyrinthulid phylogenetic group (LPG) based on 18S rDNA sequence analysis. In the hydrolysis test of labyrinthulid isolates, it was found that they could hydrolyse macromolecular compounds like starch. Ten enzymes were detected by using API-ZYM Kit in four representative isolates. Three enzymes including alkaline phosphatase, leucine arylamidase and valine arylamidase were found in higher level in API-ZYM tests. As examined their bacteriolytic activity, it was found that they could lyse only the dead cells of Gram-negative bacteria and not those of Gram-positive bacteria during incubation in both agar and liquid media. The optimum temperature range for their bacteriolysis was from 25 to 31°C. Respiratory inhibitors such as sodium cyanide, dinitrophenol and sodium azide had repressed bacteriolysis activity but no impact on viability was found in Labyrinthula cells of a strain 00–Bat-05, Philippine isolate. Orange carotenoid pigment(s) was accumulated during stationary growth phase of strain 00-Bat-05, cultured in an L-shape tube containing a bacterial dead cell suspension and concomitantly rapid cell movement of developing zoospores was observed.  
Leucine aminopeptidases (LAPs) from marine labyrinthulid strain 00-Bat-05 and thraustochytrid strain HR-3 cells were partially purified and characterized by enzymological properties. The optimum temperature of LAPs from both strains was 37°C. The thermostability of 00-Bat-05 LAP was indicated by having 80% of maximum activity after heat treatment at 60oC for 10 min, while LAP activity of strain HR-3 was completely inactivated at 60°C. LAP acvtivities from both strains were high at near pH 8.0. Both LAPs were inhibited by 1,10-phenanthroline, p-chloromercuribenzoic acid (PCMB), bestatin and sodium dodecyl sulphate (SDS), suggesting that both are SH-aminopeptidase. Enzyme activity of LAP from strain 00-Bat-05 was stimulated by Co2+ and inhibited by Zn2+, while that from HR-3 was inhibited by Co2+ and Zn2+. LAP of 00-Bat-05 had a high specificity for L-leucine-p-nitroanilide but HR-3 enzyme showed relatively broad specificity for p-nitroanilide derivatives of L-amino acids. Partially purified LAP enzyme, from labyrinthulid sp. strain 00-Bat-05, showed the bacteriolysis activity against the dead cells of Vibrio parahaemolyticus which phenomenon was also found by the cells of strain 00-Bat-05., 連合農学研究科博士論文(水産学) ; 学位取得日: 平成20年3月14日},
 title = {Studies on Bacteriolytic Activities of Marine Labyrinthulids},
 year = {}
}