Open AccessEnzymatic formation of manganese oxides by an Acremonium ‐like hyphomycete fungus, strain KR21‐2
Author(s) -
Miyata Naoyuki,
Tani Yukinori,
Iwahori Keisuke,
Soma Mitsuyuki
Publication year - 2004
Publication title -
fems microbiology ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.377
H-Index - 155
eISSN - 1574-6941
pISSN - 0168-6496
DOI - 10.1016/s0168-6496(03)00251-4
Subject(s) - biology , laccase , multicopper oxidase , manganese , strain (injury) , oxidase test , enzyme , biochemistry , chemistry , organic chemistry , anatomy
A Mn‐depositing fungus, Acremonium ‐like hyphomycete strain KR21‐2, was isolated from a Mn deposit occurring on the wall of a storage bottle containing Mn(III, IV) oxide‐coated streambed pebbles and stream water. 18S rRNA gene sequence analysis revealed that strain KR21‐2 was phylogenetically related to members of the order Hypocreales within the class Ascomycetes. The spent culture medium at the stationary phase of fungal growth contained a 54‐kDa protein capable of depositing Mn oxides. The enzymatic activity was inhibited by azide and o ‐phenanthroline. The Mn(II)‐oxidizing protein possessed a laccase activity, as indicated by direct oxidation of p ‐phenylenediamine and 2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid). These results are consistent with the role assumed for laccase‐like multicopper oxidase, which is proposed to be involved in the Mn(II)‐oxidizing factors from some bacteria. Unlike laccases of basidiomycete fungi, however, the protein of strain KR21‐2 did not produce soluble Mn(III) species in the presence of either of the Mn chelators pyrophosphate and malonate. This is the first report on the possible involvement of laccase and/or multicopper oxidase in Mn oxide deposition by ascomycetes (including their anamorphs) ubiquitous in natural environments.