Impact of Algicidal Bacillus mycoides on Diatom Ulnaria acus from Lake Baikal

Yekaterina Bedoshvili,Maria Kurilkina,Yulia Zakharova,Igor Klimenkov,Yelena Likhoshway,Nikolay Sudakov,Elvira Bayramova

doi:10.3390/d13100469

Yekaterina Bedoshvili, Maria Kurilkina + Show 5 more

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https://doi.org/10.3390/d13100469

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Abstract

Algae–bacteria interactions play an important role in water ecosystems. In this work, the BS2-15 algicidal strain was isolated from the bottom sediments of Lake Baikal and identified as Bacillus mycoides on the basis of 16S rDNA sequencing, its described ultrastructure, and biochemical properties. B. mycoides BS2-15 was demonstrated to have a strong algicidal effect against a freshwater diatom culture of Ulnaria acus, inhibiting its growth and increasing frustules fragility. By analyzing the impact of bacterial filtrate onto the cells of U. acus, we demonstrated that perhaps an algicidal compound is produced by bacteria independently in the presence of diatoms in a medium. Using methods of TUNEL and confocal microscopy, we revealed that the bacterial algicidal effect on the diatom cells results in DNA fragmentation, nucleus destruction, and neutral lipid accumulation. This phenomenon highlights the complexity of algae–bacteria interactions and their potential role in regulating water ecosystem microbial populations.

Highlights

Phytoplankton is essential for global carbon cycles [1], and diatom algae in particular have an organic carbon output comparable to that of land plants [2,3]
Along with the search for algicidal bacteria useful in preventing toxic algal blooms [5], the mechanisms of algaebacteria interactions have fundamental importance [6]; many bacterial strains have an algicidal effect on diatoms by releasing enzymes into the environment [7,8,9]
We studied the algicidal effect of B. mycoides BS2-15, a strain isolated from sediments of Lake Baikal

Summary

Introduction

Phytoplankton is essential for global carbon cycles [1], and diatom algae in particular have an organic carbon output comparable to that of land plants [2,3]. Along with the search for algicidal bacteria useful in preventing toxic algal blooms [5], the mechanisms of algaebacteria interactions have fundamental importance [6]; many bacterial strains have an algicidal effect on diatoms by releasing enzymes into the environment [7,8,9]. Bacillus spp. are Gram-positive bacteria widely distributed in the environment; this is likely because they form endospores resistant to different factors, such as drying out, UV radiation, and lack of nutrients [10,11]. B. mycoides, like many representatives of the genus Bacillus, are saprophytic organisms [13,14]

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