Молекулярно-генетическая и морфологическая характеристика Micractinium thermotolerans и M. inermum (Trebouxiophyceae, Chlorophyta) из пирокластических отложений полуострова Камчатка (Россия)

В ходе исследования разнообразия водорослей пирокластических отложений вулканов Шивелуч и Горелый (полуостров Камчатка) были выделены Chlorella-подобные штаммы зеленых водорослей VCA-72 и VCA-93 из проб, отобранных вдоль русла р. Байдарная на вулкане Шивелуч и на выходе термальных паров по краю кальдеры на южном склоне вулкана Горелый в 2018 и 2020 гг. соответственно. Идентификация штаммов выполнялась в рамках комплексного подхода микроскопическими и молекулярно-генетическими методами, включающими предварительную идентификацию, получение нуклеотидных последовательностей малой субъединицы и внутреннего транскрибируемого спейсера рРНК, построение филогенетических деревьев и вторичных структур участков ITS1 и ITS2 рРНК. На филогенетическом древе штамм VCA-93 кластеризовался в видовой кладе Micractinium thermotolerans. При сравнении моделей спиральных доменов ITS1 и ITS2 у M. thermotolerans различий не выявлено. Штамм VCA-72 занимал базальное положение в кладе M. inermum. Модели вторичной структуры спиралей штамма VCA-72 в целом были сходны с моделями для M. inermum, однако отмечена внутривидовая вариабельность, обусловленная в основном заменами в верхушечных и боковых петлях. В спиральных участках исследуемых штаммов M. inermum обнаружено пять замен hCBC, тогда как замен CBC обнаружено не было. Детальный анализ морфологии и жизненного цикла позволил выявить в стареющих культурах клетки, которые по размеру значительно превышают вегетативные и имеют грушевидную, овальную и эллипсоидную формы с неглубоким широким сужением в центре. Также в стареющих культурах обоих видов были выявлены клетки с бесцветными липидными каплями. Способность синтезировать и накапливать липиды говорит о большом потенциале штаммов для производства биодизельного топлива. Обзор местообитаний предыдущих и новых находок позволяет сделать вывод об экологической пластичности исследуемых видов. Полученные результаты дополняют сведения о биогеографии видов: M. inermum обнаружен впервые на территории России, а M. thermotolerans – на полуострове Камчатка.

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