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Page 8 of 18 Yakovleva et al. Microbiome Res Rep 2024;3:19 https://dx.doi.org/10.20517/mrr.2023.56

Figure 1. Composition of the bacterial microbiome in the fly lines adapted to the substrate with different salinity and in the
corresponding substrates. 0a, 0b, and 0c - control lines reared on a medium without salt, 2a, 2b, 2c - lines reared on a medium with 2%
NaCl, 4a, 4b, 4c - with 4% NaCl, 7a and 7b - with 7% NaCl. For each fly line, profiling was made in 2 replicates.

more resistant to increased salinity, as at 2% NaCl, its growth decreased only by 40%. L. pseudomesenteroides
was the most resistant to the salinity of the substrate compared with the other two strains. However, its
growth also decreased significantly with the increase of the media salinity. According to Tukey’s HSD test,
the difference between all groups is statistically significant, P < 0.0005.

The total number of bacteria and yeasts in the fly lines adapted to the substrate with different
salinity and in the corresponding substrates
The number of aerobic and aerotolerant bacteria in D. melanogaster homogenates of different lines
determined by direct plating varied from 10 to 10 CFU per 1 fly. The bacterial count depended on the
7
4
concentration of NaCl in the substrate, but it could differ by an order of magnitude in lines reared at the
same salt concentration [Table 1, Supplementary Table 3]. In D. melanogaster, the number of bacteria
decreased with the increase in NaCl concentration from 0% to 2%, and increased and exceeded the number
of bacteria in the control lines with an increase in NaCl from 2% to 4%. However, at 7%, it decreased again
to the level of control flies (0% NaCl). A different trend was observed in the substrate samples: the number
of bacteria was the highest on the substrate without salt and the lowest at 7% NaCl. At 4% NaCl, the number
of bacteria was higher than that at 2%, similar to the pattern observed in the flies.