Miniscule Mollicutes: Current hurdles to bacteriophage identification

Mollicutes are a diverse class of bacteria with a variety of unique characteristics that have allowed them to adapt to a range of hosts and often evade routine cultivation techniques. The focus of previous work has been on the major human pathogens; however, here we present a holistic introduction to the many other different genera that constitute the Mollicutes. They represent a significant One Health concern with limited available treatment options given their intrinsic and acquired resistance to many antibiotics. Bacteriophages (phages) are a promising therapeutic and one poorly explored in these bacteria and an avenue to understand gene transfer and resistance development. This review aims to emphasize the many unique and diverse qualities of the Mollicutes and synthesize our current understanding of phages of these bacteria and the challenges that have hindered their isolation and characterization.