Complex sentence: The recognition of "M. catarrhalis" as a pathogenic bacterium has led to studies for possible antibodies against it, which have led to a wider understanding of the composition of "M. catarrhalis".
Split into simpler sentences: The recognition of "M. catarrhalis" as a pathogenic bacterium has led to studies for possible antibodies against it. Therefore, these studies have led to a wider understanding of the composition of "M. catarrhalis".