Distribution and evolution of nisin-sucrose elements in Lactococcus lactis

Area of Science:

• Microbiology
• Molecular Biology
• Bacteriology

Background:

• Nisin and nisin Z are bacteriocins produced by Lactococcus lactis.
• Nisin-sucrose elements are mobile genetic elements involved in the spread of nisin production and immunity.
• Understanding the diversity and mobility of these elements is crucial for controlling their dissemination.

Purpose of the Study:

• To investigate the distribution, architecture, and conjugal transfer capacity of nisin-sucrose elements in wild-type Lactococcus lactis strains.
• To classify these elements based on their genetic makeup and functional properties.
• To propose a model for the evolution of nisin-sucrose elements.

Main Methods:

• Genomic DNA hybridization using probes specific to the nisin-sucrose transposon Tn5276.
• Analysis of key genetic regions including left/right ends, nisA, nisZ, and IS1068 (iso-IS904).
• Comparative analysis of element structures across 13 different Lactococcus lactis strains.

Main Results:

• Three distinct classes of nisin-sucrose elements were identified.
• Classes I and II are conjugative transposons carrying nisA and nisZ genes, respectively (e.g., Tn5276, Tn5278).
• Class III elements are non-conjugative, contain nisZ, and exhibit variations in IS1068-like element presence and orientation, suggesting rearrangement events.

Conclusions:

• The study provides a detailed classification of nisin-sucrose elements, highlighting structural diversity.
• An iso-IS1068-mediated rearrangement is proposed to explain variations in element architecture.
• The findings have practical implications for understanding and manipulating the transfer of nisin production and immunity traits.