The origin of the 'Mycoplasma mycoides cluster' coincides with domestication of ruminants

Abstract

The 'Mycoplasma mycoides cluster' comprises the ruminant pathogens Mycoplasma mycoides subsp. mycoides the causative agent of contagious bovine pleuropneumonia (CBPP), Mycoplasma capricolum subsp. capripneumoniae the agent of contagious caprine pleuropneumonia (CCPP), Mycoplasma capricolum subsp. capricolum, Mycoplasma leachii and Mycoplasma mycoides subsp. capri. CBPP and CCPP are major livestock diseases and impact the agricultural sector especially in developing countries through reduced food-supply and international trade restrictions. In addition, these diseases are a threat to disease-free countries. We used a multilocus sequence typing (MLST) approach to gain insights into the demographic history of and phylogenetic relationships among the members of the 'M. mycoides cluster'. We collected partial sequences from seven housekeeping genes representing a total of 3,816 base pairs from 118 strains within this cluster, and five strains isolated from wild Caprinae. Strikingly, the origin of the 'M. mycoides cluster' dates to about 10,000 years ago, suggesting that the establishment and spread of the cluster coincided with livestock domestication. In addition, we show that hybridization and recombination may be important factors in the evolutionary history of the cluster.

Figure 1. Population structure and phylogenetic relationship of the ‘M. mycoides cluster’ and five non-species assigned Mycoplasma strains.

The 4 populations revealed by the STRUCTURE analysis using the linkage model and 7 housekeeping sequences are displayed on the top of the figure and marked with different colours. The ancestral parts of each strain are displayed in vertical lines. Subpopulations of the M. capricolum/M. leachii population are displayed below.

Figure 2. Maximum credibility tree resulting from the BEAST analysis of the concatenated sequence alignment, as described in the main text.

Bayesian posterior probabilities are provided at the major nodes in the tree as a measure of support for clustering of the distinct strains. The scale is given in years before present.