Construction and basic characterization of deletion mutants of the genes involved in chitin utilization by Serratia marcescens 2170

Abstract

In order to elucidate the roles of ChiP, ChiQ, and ChiX in chitin utilization by Serratia marcescens 2170, the construction of single-gene deletion mutants of the chiP, chiQ, and chiX genes was attempted by allelic exchange mutagenesis. ΔchiP formed smaller clearing zones and ΔchiX formed larger ones than wild-type 2170 on an agar plate containing colloidal chitin. ΔchiP grew slowly on the lower concentration of (GlcNAc)_2, and there was essentially no growth on chitin oligosaccharides larger than (GlcNAc)₃. The gene product of chiP was detected in the outer membrane fraction, consistently with the hypothesis that chiP encodes outer membrane chitoporin. Deletion of chiQ decreased and that of chiX increased the growth rates on chitin oligosaccharides. These observations strongly suggest that all three genes are involved in chitin utilization and that the deletion mutants obtained in this study might prove useful tools to clarify the details of the chitin utilization system of this bacterium.

Graphical Abstract

Construction of single-gene deletion mutants of the chiP, chiQ, and chiX genes of Serratia marcescens 2170 was attempted by allelic exchange mutagenesis. Phenotype of the mutants indicated that all three genes play important roles in chitin utilization of this bacterium.

Key words:

• chitinase
• chitobiase
• chitoporin
• Serratia marcescens

Funding

This work was supported by Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan [grant number 24580104].

Notes

Abbreviations: GlcNAc, N-acetylglucosamine; (GlcNAc)₂, N,N′-diacetylchitobiose; 4MU, 4-methylumbelliferon.