Reducing the Bacterial Lag Phase Through Methylated Compounds: Insights from Algal-Bacterial Interactions

Abstract

Short lag times are beneficial for heterotrophic bacteria that compete for resources in environments with fluctuating organic carbon levels. We found that the marine model bacterium Phaeobacter inhibens achieves shorter lag times in the presence of nano- to micromolar concentrations of N- or S-methylated compounds, which are abundantly produced by microalgae. To understand the underlying mechanism, we studied algal-bacterial co-cultures and bacterial pure cultures during their lag phase using transcriptomics analyses, 13C-labeled metabolomics, gene knock-out experiments and enzymatic characterizations. Our findings highlight methyl group synthesis as a bottleneck during the bacterial lag phase, which can be overcome by assimilating methyl groups from external sources. Our study reveals a fundamental aspect of the bacterial lag phase, emphasizing the importance of studying bacterial physiology within an ecological framework, particularly in the context of microbial interactions.

Bacteria Contribute Exopolysaccharides to an Algal-Bacterial Joint Extracellular Matrix

“…To test whether improved bacterial attachment is the result of increased growth, we monitored bacterial growth until stationary phase in cultures supplemented with algal exudates versus ASW. in Our data showed that bacteria supplemented with spent medium exhibited earlier transition to logarithmic growth as previously reported 69 (Fig. S1), however these cultures reached maximal cell numbers that are slightly lower than cultures grown in ASW.…”

“…ΔexoY mutant showed similar growth to WT both when supplemented with SEA or untreated. both ΔexoY and WT bacteria showed shorter lag-phases in response to the SEA treatment, as previously described 69 . Maximum O.D.…”

“…Lines represent the mean of n = 6 biological repeats with shaded error bars. DMSP, betaine, succinate and SEA expedited the bacterial lag-phase compared to the control, as previously described 69 . However, the maximum O.D.…”

“…Lines represent the mean of n=6 biological repeats with shaded error bars. All concentrations of spent medium induced lag-phase shortening compared to ASW (0%), as previously described 69 . However, the maximum O.D.…”

“…Our model system includes the algal strain Emiliania huxleyi and the bacterial species Phaeobacter inhibens. This algal-bacterial model system was previously studied by us 59,63,[66][67][68][69] and by others [70][71][72][73][74] , revealing many routes of interactions and their environmental importance. Bacteria of the P. inhibens species attach through their pole to both abiotic and biotic surfaces 62,67 , including direct attachment to E. huxleyi cells 59 .…”