R. microsporus ATCC52814 asexual sporulation on PDA. Photo by Stephen Mondo

DAPI stained hypha of R. microsporus ATCC52814 harboring YFP labeled Burkholderia endosymbionts. Fungal nuclei are shown in blue and endosymbionts in green. Photo by Olga Lastovetsky

Rhizopus microsporus ATCC52814 is a member of the Mucoromycotina and is one of the few fungal lineages currently described to harbor bacterial endosymbionts. The endosymbiont, Burkholderia rhizoxinica, exhibits signs of genome reduction, as its 3.75 Mb genome is less than half the size of typical free-living Burkholderia. Despite this, both host and endosymbiont can be cultivated independently and the symbiosis can be re-established under laboratory conditions, making this an attractive model system for understanding the molecular underpinnings of fungal-bacterial symbioses. R. microsporus ATCC52814 (sex '-') is the opposite mate of R. microsporus ATCC52813 (sex '+'), a strain already sequenced by the JGI, and was imported as part of a larger CSP which will use comparative genomics to better understand early diverging terrestrial fungi and their bacterial endosymbionts.