Two chitin deacetylases, Cda1 and Cda2, from Coprinopsis cinerea were expressed and characterized. Cda1 preferably deacetylates the nonreducing end residue of (GlcNAc)₂, the internal or nonreducing end residue of (GlcNAc)₃ and the nonreducing residue of (GlcNAc)₆ after deacetylating the internal residues. In contrast, Cda2 preferably deacetylates the reducing end residue of (GlcNAc)₂, the internal or reducing end residue of (GlcNAc)₃ and the reducing residue of (GlcNAc)₆ after deacetylating the internal residues. Furthermore, Cda1 prefers chitohexaose with higher degrees of acetylation for deacetylation, while Cda2 shows a weaker preference for chitohexaose with varying degrees of acetylation. The predicted Cda1 structure shows more hydrophobic aromatic amino acids on the surface near subsite +1 in the active site than on the surface near subsite −1, whereas the predicted Cda2 structure has more hydrophobic aromatic amino acids on the surface near subsite −1 than on the surface near subsite +1, which may be the molecular basis of the distinctive catalytic features between Cda1 and Cda2. Notably, Cda1 has a high transcription level in the nonelongating basal stipe region, whereas Cda2 has a high transcription level in the elongating apical stipe region, and the transcription level of the former is approximately five times that of the latter. Correspondingly, the molar ratio of GlcN/GlcNAc increased from 0.15 in the cell wall of the apical stipe region to 0.22 in the cell wall of the basal stipe region. Different modes of action of Cda1 and Cda2 may be related to their functions in the different stipe regions.

Corallococcus sp. strain EGB is a Gram-negative myxobacteria isolated from saline soil, and has considerable potential for the biocontrol of phytopathogenic fungi. However, the detailed mechanisms related to development and predatory behavior are unclear. To obtain a comprehensive overview of genetic features, the genome of strain EGB was sequenced, annotated, and compared with 10 other Corallococcus species. The strain EGB genome was assembled as a single circular chromosome of 9.4 Mb with 7916 coding genes. Phylogenomics analysis showed that strain EGB was most closely related to Corallococcus interemptor AB047A, and it was inferred to be a novel species within the Corallococcus genus. Comparative genomic analysis revealed that the pan-genome of Corallococcus genus was large and open. Only a small proportion of genes were specific to strain EGB, and most of them were annotated as hypothetical proteins. Subsequent analyses showed that strain EGB produced abundant extracellular enzymes such as chitinases and β-(1,3)-glucanases, and proteases to degrade the cell-wall components of phytopathogenic fungi. In addition, 35 biosynthetic gene clusters potentially coding for antimicrobial compounds were identified in the strain EGB, and the majority of them were present in the dispensable pan-genome with unexplored metabolites. Other genes related to secretion and regulation were also explored for strain EGB. This study opens new perspectives in the greater understanding of the predatory behavior of strain EGB, and facilitates a potential application in the biocontrol of fungal plant diseases in the future.