Kinopus chlorellivorus gen. nov., sp. nov. (Vampyrellida, Rhizaria), a New Algivorous Protist Predator Isolated from Large-Scale Outdoor Cultures of Chlorella sorokiniana

• Published in: Applied and environmental microbiology 2022-11, Vol.88 (22), p.e0121522-e0121522
• Main Authors: Zhang, Hanwen, Patterson, David J, He, Yue, Wang, Hongxia, Yuan, Danni, Hu, Qiang, Gong, Yingchun
• Format: Article
• Language: English
• Subjects: Algae; Amoeba; Biomass; Cell culture; Cercozoa - genetics; Chlorella; Chlorella sorokiniana; Contaminants; DNA sequencing; Environmental Microbiology; Grazing; Growth rate; Inclusions; Ingestion; Microalgae; Microorganisms; New genera; New species; Predators; Prey; Resting stages; Rhizaria; rRNA; Scenedesmus; Spotlight Selection; Transmission electron microscopy
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/aem.01215-22

The large-scale culture of low-cost algal biomass can be significantly affected by microbial grazing on the algae. To minimize the impact, it is necessary to manage the predators. In this study, we describe a new genus and species of vampyrellid amoeba, Kinopus chlorellivorus, which caused the loss of Chlorella sorokiniana in large-scale cultures. We assigned it to the family Leptophryidae (Vampyrellida) based on morphology and small-subunit (SSU) rRNA gene sequence comparisons. Using transmission electron microscopy, we found spherical lucent inclusions, which have not been reported for any leptophryids or other vampyrellids. The gene sequence of SSU rRNA did not match any recognized genera or species and contained four characteristic regions. preys on algae by engulfment. Laboratory feeding experiments confirmed that its grazing rate was as high as 131 cells day individual . Results of prey-range experiments demonstrated that it could consume other chlorophyte microalgae (e.g., , , and ) but with a strong feeding ability on spp., with ingestion rates ranging from 2.67 to 3.15 prey predator h and growth rates of the amoeba ranging from 0.039 to 0.045 h . On the basis of its high grazing ability on , capacity to form large populations in a short period of time, and capacity to form resistant resting stages, this contaminant has the potential to cause serious problems in large-scale culture and should be of concern to operators of algal production facilities. The vampyrellids (Vampyrellida, Rhizaria) are a major group of predatory amoebae that have attracted significant attention because of their diversity of feeding strategies. The crucial roles they play in important processes such as suppressing soil disease and controlling aquatic algae, and as microbial contaminants in outdoor large-scale algal cultures, have also received increasing attention. In this study, a new genus and species of algivorous vampyrellid amoeba, , is described as a significant grazer responsible for losses in outdoor industrial cultures. We found that the amoeba's detrimental effects on cultures may be related to its specific feeding characteristics. This study provides phenotypic and genetic information on a previously unknown vampyrellid, emphasizes the impact of contaminating vampyrellids in commercial microalgal cultures, and will contribute to the development of management strategies for predicting this kind of contaminant in large-scale microalgal cultivation.