当前位置： SCI文献检索 > JOURNAL OF BACTERIOLOGY期刊下所有文献 > The C-Terminal Zwitterionic Sequence of CotB1 Is Essential for Biosilicification of the Bacillus cereus Spore Coat.

The C-Terminal Zwitterionic Sequence of CotB1 Is Essential for Biosilicification of the Bacillus cereus Spore Coat.

Abstract：

UNLABELLED:Silica is deposited in and around the spore coat layer of Bacillus cereus, and enhances the spore's acid resistance. Several peptides and proteins, including diatom silaffin and silacidin peptides, are involved in eukaryotic silica biomineralization (biosilicification). Homologous sequence search revealed a silacidin-like sequence in the C-terminal region of CotB1, a spore coat protein of B. cereus. The negatively charged silacidin-like sequence is followed by a positively charged arginine-rich sequence of 14 amino acids, which is remarkably similar to the silaffins. These sequences impart a zwitterionic character to the C terminus of CotB1. Interestingly, the cotB1 gene appears to form a bicistronic operon with its paralog, cotB2, the product of which, however, lacks the C-terminal zwitterionic sequence. A ΔcotB1B2 mutant strain grew as fast and formed spores at the same rate as wild-type bacteria but did not show biosilicification. Complementation analysis showed that CotB1, but neither CotB2 nor C-terminally truncated mutants of CotB1, could restore the biosilicification activity in the ΔcotB1B2 mutant, suggesting that the C-terminal zwitterionic sequence of CotB1 is essential for the process. We found that the kinetics of CotB1 expression, as well as its localization, correlated well with the time course of biosilicification and the location of the deposited silica. To our knowledge, this is the first report of a protein directly involved in prokaryotic biosilicification. IMPORTANCE:Biosilicification is the process by which organisms incorporate soluble silicate in the form of insoluble silica. Although the mechanisms underlying eukaryotic biosilicification have been intensively investigated, prokaryotic biosilicification was not studied until recently. We previously demonstrated that biosilicification occurs in Bacillus cereus and its close relatives, and that silica is deposited in and around a spore coat layer as a protective coating against acid. The present study reveals that a B. cereus spore coat protein, CotB1, which carried a C-terminal zwitterionic sequence, is essential for biosilicification. Our results provide the first insight into mechanisms required for biosilicification in prokaryotes.

journal_name

J Bacteriol

journal_title

Journal of bacteriology

authors

Motomura K,Ikeda T,Matsuyama S,Abdelhamid MA,Tanaka T,Ishida T,Hirota R,Kuroda A

doi

10.1128/JB.00447-15

subject

Has Abstract

pub_date

2015-10-26 00:00:00

pages

276-82

issue

eissn

0021-9193

issn

1098-5530

pii

JB.00447-15

journal_volume

198

pub_type

杂志文章

在线工具

The C-Terminal Zwitterionic Sequence of CotB1 Is Essential for Biosilicification of the Bacillus cereus Spore Coat.