Escherichia coli Culture Filtrate Enhances the Growth of Gemmata spp.

Abstract

BackgroundPlanctomycetes bacteria are known to be difficult to isolate, we hypothesized this may be due to missing iron compounds known to be important for other bacteria. We tested the growth-enhancement effect of complementing two standard media with Escherichia coli culture filtrate on two cultured strains of Gemmata spp. Also, the acquisition of iron by Gemmata spp. was evaluated by measuring various molecules involved in iron metabolism.Materials and MethodsGemmata obscuriglobus and Gemmata massiliana were cultured in Caulobacter and Staley’s medium supplemented or not with E. coli culture filtrate, likely containing siderophores and extracellular ferrireductases. We performed iron metabolism studies with FeSO4, FeCl3 and deferoxamine in the cultures with the E. coli filtrate and the controls.Results and DiscussionThe numbers of G. obscuriglobus and G. massiliana colonies on Caulobacter medium or Staley’s medium supplemented with E. coli culture filtrate were significantly higher than those on the standard medium (p < 0.0001). Agar plate assays revealed that the Gemmata colonies near E. coli colonies were larger than the more distant colonies, suggesting the diffusion of unknown growth promoting molecules. The inclusion of 10–4 to 10–3 M FeSO4 resulted in rapid Gemmata spp. growth (4–5 days compared with 8–9 days for the controls), suggesting that both species can utilize FeSO4 to boost their growth. In contrast, deferoxamine slowed down and prevented Gemmata spp. growth. Further studies revealed that the complementation of Caulobacter medium with E. coli culture filtrate and 10–4 M FeSO4 exerted a significant growth-enhancement effect compared with that obtained with Caulobacter medium supplemented with E. coli culture filtrate alone (p < 0.0122). Moreover, the intracellular iron concentrations in G. obscuriglobus and G. massiliana cultures in iron-depleted broth supplemented with the E. coli filtrate were 0.63 ± 0.16 and 0.78 ± 0.12 μmol/L, respectively, whereas concentrations of 1.72 ± 0.13 and 1.56± 0.11 μmol/L were found in the G. obscuriglobus and G. massiliana cultures grown in broth supplemented with the E. coli filtrate and FeSO4. The data reported here indicated that both E. coli culture filtrate and FeSO4 act as growth factors for Gemmata spp. via a potentiation mechanism.

Planctomycetes as Host-Associated Bacteria: A Perspective That Holds Promise for Their Future Isolations, by Mimicking Their Native Environmental Niches in Clinical Microbiology Laboratories

“…Testing co-culture of Gemmata spp. with E. coli filtrate, we showed that the number of both G. obscuriglobus and Gemmata massiliana colonies were significantly higher on basic medium supplemented with E. coli filtrate than on the standard medium (p < 0.0001) (Kaboréet al, 2019a). Hence, cooperating groups might exist between uncultured Planctomycetes and Proteobacteria like E. coli for siderophore and iron acquisition, which causes the interests of these individuals to be associated with those of the group and other such as Verrucomicrobia and Actinobacteria (D'Onofrio et al, 2010).…”

Screening for Biofilm-Stimulating Factors in the Freshwater Planctomycete Planctopirus limnophila to Improve Sessile Growth in a Chemically Defined Medium

“…LF2 revealed that Cu is more toxic than Zn at the same concentration [59], which also appeared to be the case for P. limnophila based on our OD 600 measurements in the liquid phase. However, the MTT assay for Cu (50) and the crystal violet staining for Cu (50) and Cu (100) generated higher absorbance values compared to Zn, indicating a stronger positive effect on sessile growth. The stabilizing effect of cationic metal ions, such as Cu, Zn, and Fe, on B. subtilis biofilms has been previously demonstrated [55].…”

“…In earlier studies, the growth of Gemmata spp. was enhanced by the addition of FeSO 4 [50] and two planctomycetal strains isolated from Fe(OH) 2 deposits were found to be attached to Fe precipitates [51]. Fe promotes biofilm formation in Pseudomonas aeruginosa [52,53], Escherichia coli [54], Bacillus subtilis [55], Staphylococcus aureus [56], and Vibrio cholerae [57].…”

“…The metal ion content of the medium was increased by adding three different concentrations of Fe, Cu, and Zn. MTT assays indicated a significant increase in absorbance for the media supplemented with Fe (50), Fe (500), and Cu (50), indicating that these concentrations enhanced surface colonization (Figure 2A). Crystal violet staining confirmed the results for Fe (50) and Cu (50), whereas Fe (500) instead showed a decline in absorbance (Figure 2B).…”

“…MTT assays indicated a significant increase in absorbance for the media supplemented with Fe (50), Fe (500), and Cu (50), indicating that these concentrations enhanced surface colonization (Figure 2A). Crystal violet staining confirmed the results for Fe (50) and Cu (50), whereas Fe (500) instead showed a decline in absorbance (Figure 2B). However, crystal violet staining revealed a significant increase in absorbance for Fe (100) and Cu (100), the former also showing an increase in the MTT assay but the latter showing a decrease in the MTT assay.…”