Comparative biogeography of Chromobacterium from the neotropics

Abstract

The genus Chromobacterium encompasses free-living Gram-negative bacteria. Until 2007, the genus consisted of only one species but six species are now recognized. Chromobacterium violaceum is the type species of the genus and is commonly found in soil and water in tropical and sub-tropical regions. We have investigated a collection of 111 isolates displaying violet pigmentation from undisturbed aquatic and soil environments from Brazilian Cerrado ecosystem. The 16S rRNA gene phylogeny revealed that all isolates were allocated in a monophyletic cluster inside the Chromobacterium genus and formed few clusters related most closely with Chromobacterium piscinae. The two sets of isolates from water and soil were analyzed by the repetitive extragenic palindromic (rep)-PCR genomic fingerprinting technique using a BOX-AR1 primer. The antimicrobial susceptibility and the different carbon sources utilized by these isolates were also investigated. Physiological profiles of the isolates generated by BIOLOG GN2 plates showed great versatility in the substrate utilization, much higher than the C. violaceum ATCC 12472. All isolates exhibited a high minimum inhibitory concentration (MIC) to ampicillin (MIC > 512 μg/ml) and were inhibited by ciprofloxacin, tetracycline and mercury at the lowest concentration tested (MIC < 2 μg/ml). Thirteen BOX-PCR band patterns were identified from 33 individual fingerprints. Eleven patterns provided evidence for endemic distributions. Antimicrobial susceptibility and BOX-PCR fingerprint clustering showed a clear distinction between Chromobacterium isolates from the water and soil. The results suggested that microenvironment barriers such as water and soil can play an important role in the periodic selection and diversification of Chromobacterium population ecotypes.

Inflammasomes Coordinate Pyroptosis and Natural Killer Cell Cytotoxicity to Clear Infection by a Ubiquitous Environmental Bacterium

“…C. violaceum is a ubiquitous environmental organism that inhabits aquatic environments in the tropics and subtropics (Lima-Bittencourt et al, 2010). It encodes two T3SSs, Cpi-1 and Cpi-2, with similarity to the S. typhimurium SPI-1 and SPI-2 T3SS, respectively (Brito et al, 2004; Miki et al, 2010).…”

A scalable metabolite supplementation strategy against antibiotic resistant pathogen Chromobacterium violaceum induced by NAD+/NADH+ imbalance

“…The detailed description of the model can be found in Additional file 5. The model was initially validated using a set of 10 substrate utilization BIOLOG GN2 plate data existing in literature [43–45]. …”

Polyphasic identification of isolates of Chromobacterium sp. obtained from flooded soil

“…However, the 16S rRNA is considered a neutral marker, used to distinguish bacteria to the species level according to their evolutionary history of common ancestry, although with some limitations (Oren, 2004). The characterization of bacteria can be effectively performed by identifying and characterizing the sequence information obtained from the 16S rDNA of several samples of Chromobacterium sp., as previously accomplished by Lima-Bittencourt et al (2011).…”

“…Thus, the 16S rDNA must be used, preferably in studies of taxonomy and phylogeny, with an effort to deposit a large number of these sequences related to other ribosomal genes. Sequencing of the 16S rDNA gene has been frequently used as a molecular marker, making this sequence useful in the genomic fingerprinting of bacteria (Lima-Bittencourt et al, 2011) Corroborating the results of the authors cited in the Stackebrandt and Goebel (1994) proposed a similarity in the sequences of ≥97% for delimiting bacterial species. However, the 16S rRNA is considered a neutral marker, used to distinguish bacteria to the species level according to their evolutionary history of common ancestry, although with some limitations (Oren, 2004).…”