Random gene shuffling drives the mysterious variations in the virulence of pneumococci, the bacteria responsible for a significant proportion of pneumonia and bacterial meningitis cases, reports a study published online in Nature Communications. The findings may have broad implications in the infectious disease field, as similar genes exist in other pathogenic bacteria.
In general, pneumococci are common, harmless inhabitants of our nose and throat but they can also cause serious infections, especially in children and immunocompromised people. Their alternation between harmless and highly virulent forms has been known since the 1930s, but the underlying mechanism for this switch was unclear.
Marco Oggioni, Michael Jennings and colleagues show that the culprit behind this Jekyll-and-Hyde behaviour is a cluster of genes that frequently undergoes random rearrangements, resulting in any of six alternative states. Each state drives the methylation of different DNA sequences across the bacterial genome, which affects the expression of many genes that determine virulence and other properties.
Further research is required to explore the mechanism underlying the random gene shuffling and to determine whether similar processes are involved in gene regulation in other bacteria.