Atomic force microscopy reveals a morphological differentiation of chromobacterium violaceum cells associated with biofilm development and directed by N-hexanoyl-L-homoserine lactone

• Published in: PloS one Vol. 9; no. 8; p. e103741
• Main Authors: Kamaeva, Anara A, Vasilchenko, Alexey S, Deryabin, Dmitry G
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 11.08.2014; Public Library of Science (PLoS)
• Subjects: 4-Butyrolactone - analogs & derivatives; 4-Butyrolactone - pharmacology; Adaptability; Atomic force microscopy; Atomic structure; Bacteria; Bacteriology; Binding sites; Biofilms; Biofilms - drug effects; Biofilms - growth & development; Biology and Life Sciences; Biomass; Biosynthesis; Cell Differentiation - drug effects; Chromobacterium - cytology; Chromobacterium - drug effects; Chromobacterium - genetics; Chromobacterium - physiology; Chromobacterium violaceum; Cytology; Cytoplasmic membranes; Differentiation; Ethanol; Extrusion; Gene expression; Genomes; Growth rate; Homoserine lactones; Invaginations; Microscopy; Microscopy, Atomic Force; Morphology; Motility; Mutation; Pathogenicity; Pathogens; Pseudomonas aeruginosa; Quorum Sensing - drug effects; Signal transduction; Soil water; Violacein; United Kingdom > UK; United States > US; Russia
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0103741

Chromobacterium violaceum abounds in soil and water ecosystems in tropical and subtropical regions and occasionally causes severe and often fatal human and animal infections. The quorum sensing (QS) system and biofilm formation are essential for C. violaceum's adaptability and pathogenicity, however, their interrelation is still unknown. C. violaceum's cell and biofilm morphology were examined by atomic force microscopy (AFM) in comparison with growth rates, QS-dependent violacein biosynthesis and biofilm biomass quantification. To evaluate QS regulation of these processes, the wild-type strain C. violaceum ATCC 31532 and its mini-Tn5 mutant C. violaceum NCTC 13274, cultivated with and without the QS autoinducer N-hexanoyl-L-homoserine lactone (C6-HSL), were used. We report for the first time the unusual morphological differentiation of C. violaceum cells, associated with biofilm development and directed by the QS autoinducer. AFM revealed numerous invaginations of the external cytoplasmic membrane of wild-type cells, which were repressed in the mutant strain and restored by exogenous C6-HSL. With increasing bacterial growth, polymer matrix extrusions formed in place of invaginations, whereas mutant cells were covered with a diffusely distributed extracellular substance. Thus, quorum sensing in C. violaceum involves a morphological differentiation that organises biofilm formation and leads to a highly differentiated matrix structure.