Improved culture of fastidious Gemmata spp. bacteria using marine sponge skeletons

Gemmata are Planctomycetes bacteria recalcitrant to traditional cultivation in the clinical microbiology laboratory and they have been seldom documented in patients. Based on previously known relationships of Planctomycetes with marine sponges, we designed a new culture medium A incorporating marine sponge skeleton of Spongia sp. to the standard culture medium; and culture medium B incorporating Spongia sp. skeleton heat aqueous filtrate into medium A; and inoculating the three culture media (standard, A and B) with Gemmata obscuriglobus DSM 5831 T and Gemmata massiliana DSM 26013 T in the presence of negative controls. Cultures were observed by naked eyes for 7 days and bacterial growth was quantified by microscopic observations and culture-based enumerations. Macroscopic observations at day-3 revealed a pink bacterial pellet in medium B tubes while standard medium tubes remained limpid until day-8. Growing Gemmata spp. bacteria in medium A yielded air bubbles released by bacterial respiration, whereas control tubes remained bubble-free. The number of colonies in standard medium (1.363 ± 115 for G . obscuriglobus , 1.288 ± 83 for G . massiliana ) was significantly lower than those counted from medium B (2.552 ± 128 for G . obscuriglobus , 1.870 ± 112 for G . massiliana ) and from medium A (2.851 ± 137 for G . obscuriglobus , 2.035 ± 163 for G . massiliana ) (p