Effects of the histone-like protein HU on cellulose degradation and biofilm formation of Cytophaga hutchinsonii
Cytophaga hutchinsonii, belonging to Bacteroidetes, is speculated to use a novel cell-contact mode to digest cellulose. In this study, we identified a histone-like protein HU, CHU_2750, in C. hutchinsonii, whose transcription could be induced by crystalline but not amorphous cellulose. We constructed a CHU_2750-deleted mutant and expressed CHU_2750 in Escherichia coli to study the gene’s functions. Our results showed that although the deletion of CHU_2750 was not lethal to C. hutchinsonii, the mutant displayed an abnormal filamentous morphology, loose nucleoid, and obvious defects in the degradation of crystalline cellulose and cell motility. Further study indicated that the mutant displayed significantly decreased cell surface and intracellular endoglucanase activities but with β-glucosidase activities similar to the wild-type strain. Analyses by real-time quantitative PCR revealed that the transcription levels of many genes involved in cellulose degradation and/or cell motility were significantly downregulated in the mutant. In addition, we found that CHU_2750 was important for biofilm formation of C. hutchinsonii. The main extracellular components of the biofilm were analyzed, and the results showed that the mutant yielded significantly less exopolysaccharide but more extracellular DNA and protein than the wild-type strain. Collectively, our findings demonstrated that CHU_2750 is important for cellulose degradation, cell motility, and biofilm formation of C. hutchinsonii by modulating transcription of certain related genes, and it is the first identified transcriptional regulator in these processes of C. hutchinsonii. Our study shed more light on the mechanisms of cellulose degradation, cell motility, and biofilm formation by C. hutchinsonii.
KeywordsCytophaga hutchinsonii Histone-like protein HU Cellulose degradation Biofilm
We are grateful to Dr. Mark J. McBride (University of Wisconsin-Milwaukee, USA) for providing C. hutchinsonii ATCC 33406. We sincerely thank Dr. Haiyan Yu and Dr. Xiaomin Zhao (Analysis & Testing Center of State Key Laboratory of Microbial Technology, Shandong University) for assistance in the SEM test. We sincerely thank Dr. Taiyong Quan (Shandong University) and Mr. Long Ma (Qilu Normal University) for assistance in the CLSM test. Thanks to Dr. Edward C. Mignot and Dr. Junshu Wang (Shandong University) for linguistic advice.
This study was funded by the National Natural Science Foundation of China (grant numbers 31770080 and 31371262).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
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