Abstract
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 5831T and Gemmata massiliana DSM 26013T 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 < 0.10−4) at day-2 incubation. At day-3 incubation, the number of colonies counted from supplemented media A and B increased up to one log than those counted from the control medium (p < 0.10−4). Along the following day-4–7 incubation, the number of colonies counted from media A and B remained significantly higher compared to standard medium (p < 0.10−4). These data indicate that incorporation of spongin-based marine sponge skeleton and heat aqueous filtrate of sponge skeleton significantly improved growth of Gemmata spp. bacteria. These observations pave the way towards improved isolation and culture of Gemmata spp. from environmental and clinical specimens.
Highlights
Bacteria of the genus Gemmata, phylum Planctomycetes[1] form a group of organisms of interest in environmental sciences and medicine[2]
The pink pellet appeared at day-3 (G. obscuriglobus) and day-4 (G. massiliana) in the medium B, while it appeared at day 7–8 for G. obscuriglobus and at day 10–11 for G. massiliana in control medium
The fact that the foam that appeared at the beginning of the experiment did not appear at day-14 post-inoculation suggested that some molecules, which formed this foam, were completely consumed by the bacteria or bacterial growth has induced an inhibition of this foam, due to the releasing of acid toxic products pH (3.5–4) in the medium
Summary
Bacteria of the genus Gemmata, phylum Planctomycetes[1] form a group of organisms of interest in environmental sciences and medicine[2] In the environment, these organisms have been detected in soil, freshwater and marine habitats[3,4,5,6,7]. The holdfast of marine bacteria can form temporal or permanent junctions to stabilize the biofilm[20,21] and may help Gemmata organisms to ensure a rapid growth and their reproduction by budding[8,22,23] Based on these knowledges, we hypothesized that creating in the laboratory an attached-living style using dead marine sponge tissues (spongin) may act as a growth-promoting condition to improve the culturabily of Gemmata organisms. We sought to test the growth-enhancement effect of complementing Gemmata species standard culture medium with marine sponge filtrate and sponge small fractions as a solid phase to mimic planctomycetes natural environment in order to develop a new biphasic culture system for Gemmata spp. bacteria
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