Aerobic growth of Anoxybacillus pushchinoensis K1T: emended descriptions of A. pushchinoensis and the genus Anoxybacillus

Summary auto-generated

This study reports corrections to the taxonomic descriptions of Anoxybacillus pushchinoensis strain K1T and the genus Anoxybacillus. During authentication at the American Type Culture Collection, researchers discovered that A. pushchinoensis K1T could grow under aerobic conditions, contrary to its original classification as an obligate anaerobe. Experiments demonstrated that the strain preferentially grew anaerobically but tolerated oxygen exposure. When cultivated aerobically in alkaline medium, growth initiated at the tube bottom and resazurin was reduced due to hydrogen gas production. The strain remained catalase-negative and grew optimally at pH 9.0–9.7 in alkaline medium, but failed to survive in neutral pH media after a single passage. Based on these findings, the authors emended the species description from obligate anaerobe to aerotolerant anaerobe and updated the genus Anoxybacillus description to include both aerotolerant anaerobes and facultative anaerobes. The emended genus description also confirms that cells are rod-shaped, Gram-positive, spore-forming, alkaliphilic or alkalitolerant thermophiles with fermentative metabolism and DNA G+C content of 42–57 mol%.

Key findings

A. pushchinoensis K1T is aerotolerant rather than obligately anaerobic, capable of growth under aerobic conditions while preferring anaerobic growth
The strain is catalase-negative and produces hydrogen gas during aerobic growth, reducing resazurin indicator
A. pushchinoensis requires alkaline pH (9.0–9.7) for optimal growth and cannot survive neutral pH conditions after one passage
The genus Anoxybacillus description was emended to include aerotolerant anaerobes and facultative anaerobes rather than only obligate anaerobes

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Abstract

In this work, corrections are made to the descriptions of the species Anoxybacillus pushchinoensis corrig. and the genus Anoxybacillus. Experiments to determine the relationship of A. pushchinoensis K1^T to oxygen showed that it was capable of aerobic growth, but preferred to grow anaerobically. During aerobic growth, the redox indicator resazurin was reduced as a result of hydrogen gas production. The facultatively anaerobic nature of K1^T was ascertained by cultivation in aerobic liquid medium, where growth began at the bottom of the tube. The anaerobic nature of K1^T was also indicated by a negative catalase reaction. This work is submitted to correct the description of the species A. pushchinoensis from obligate anaerobe to aerotolerant anaerobe and to emend the description of the genus Anoxybacillus from obligate anaerobes or facultative anaerobes to aerotolerant anaerobes or facultative anaerobes.