Unusual pattern of bacterial ice nucleation gene evolution

Area of Science:

• Microbiology
• Evolutionary Biology
• Genetics

Background:

• Bacterial ice nucleation activity (INA+ phenotype) is determined by the ina gene.
• The ina gene's distribution is sparse across bacterial genera, suggesting an unusual evolutionary trajectory.
• Previous studies indicated that the ina gene's presence varies even within bacterial species.

Purpose of the Study:

• To investigate the evolutionary path of the bacterial ina gene.
• To determine if the ina gene's distribution is linked to horizontal gene transfer.
• To analyze the phylogenetic relationships of bacteria possessing the ina gene.

Main Methods:

• Southern blot analyses were used to detect the ina gene in bacterial strains.
• Ice-nucleating ability assays were performed on bacterial isolates.
• Phylogenetic analysis of 16S ribosomal RNA (rRNA) gene sequences was conducted.
• Sequence analysis of the ina gene and flanking regions was performed.

Main Results:

• The ina gene was found to be present in some strains but absent in others within four bacterial species.
• Phylogenetic analysis revealed that ina+ bacteria were not monophyletic, but interspersed among ina- bacteria.
• Inferred relationships from ina gene sequences did not align with those from 16S rRNA gene sequences.

Conclusions:

• The genotypic dimorphism of the ina gene suggests an anomalous evolutionary pattern.
• The findings support the hypothesis of horizontal gene transfer in the evolution of bacterial ina genes.
• This study highlights the dynamic nature of bacterial gene evolution and adaptation.