Moderately acid-tolerant Nitrospira strains obtained by single-colony isolation on plates

Three moderately acid-tolerant Nitrospira strains were isolated from activated sludge and sediment within one year, forming single colonies on common gelling-agent plates in 25–60 days.

• Why it matters: Cultivating Nitrospira and obtaining pure cultures has typically taken years, limiting access to lineage-specific physiology and genetics.
• What they did: Using conventional single-colony isolation, the authors plated samples on agar, agarose, and gellan gum and then applied phylogenetic/phylogenomic analyses plus acid- and oxygen-tolerance assays and comparative transcriptomics.
• The result: All three strains tolerated pH down to 5.0, with strain Z02 retaining 74% activity at pH 5.5 and 78%/85% growth-rate at 1%/21% O2, and Z02 showed acid-induced stress, envelope, and type IVa pilus gene upregulation.

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