Biofilm bacterial dynamics and changes in inorganic nitrogen density due to the presence of freshwater pearl mussels

The significance of all life can be left in traceable way: Freshwater pearl mussels
Effect of presence or absence of Margaritifera laevis or Margaritifera togakushiensis (ML/MT) on the amount of inorganic compounds and bacterial flora composition of neighboring biofilms (control: C). (a) Ammonia nitrogen concentration, (b) Nitrate nitrogen concentration, (c) Bacterial flora composition. Error bars indicate standard deviation. The * in (c) is significantly different by Student's t-test (p <0.05). From the data of (a) and (b), the concentration of inorganic nitrogen in the river biofilm is low in the presence of Margaritifera, and from the data of (c), the distribution of photosynthetic bacteria in the biofilm is particularly different. These findings suggest that the energy metabolism of the organisms constituting the biofilm are different. Credit: Kayano Takeuchi, Motoi Takeuchi, Wataru Kakino, Yutaka Uyeno

Freshwater pearl mussels are found in rivers in Japan. They are in severe decline, however, and are on the endangered Red List designated by the Ministry of the Environment. Freshwater pearl mussels are known to play an important role in the biochemical ecosystem of river nutrients in the area and downstream. Kayano Takeuchi, graduated from the Faculty of Agriculture, Shinshu University, and her father Motoi Takeuchi, strived to collect water samples and biofilm from 14 rivers throughout Japan in order to study the species and the ecosystem non-invasively. They used ceramic tiles to collect biofilm and used next-generation sequencing of bacterial 16S rRNA gene amplicons of biofilms and analyzed the genomic DNA extracted from the samples, inorganic nitrogen compounds, and chlorophyll concentration.

The research group found that in where the mussels were present, there was a significant difference in ammonia as well as nitrate in the compared to streams where no mussels were present. The bacteria belonging to Bacteroidales in Baceroidetes and Clostridiales in Firmicutes were predominantly found in the samples where the mussels were present. The mussels may help alleviate nitrogen deficiencies by playing a role in the distribution, storage, and recycling of nutrients. The mussel and no-mussel sites were similar in size and water chemistry.

Professor Yutaka Uyeno hopes that this study confirms the notion that all life's significance can be evidenced with quantitative, scientific devices. We still have much to learn about the role of biodeposits in nutrient dynamics. More intensive investigations are needed to clarify the link between freshwater pearl mussels and their ecosystems. Only in the rivers where the mussels are, were bacteria diverse.

The research was published in the journal, mSphere.

The significance of all life can be left in traceable way: Freshwater pearl mussels
An example of a preliminary survey site (left, middle) upstream of the Sakasa river in Nagano Prefecture and Margaritifera togakushiensis (right; due to modification of the survey site being prohibited, the length of the mussel bodies was measured and immediately restored with the presence of the manager. Credit: Kayano Takeuchi, Motoi Takeuchi, Wataru Kakino, Yutaka Uyeno

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More information: Kayano Takeuchi et al, Biofilm Bacterial Dynamics and Changes in Inorganic Nitrogen Density Due to the Presence of Freshwater Pearl Mussels, mSphere (2022). DOI: 10.1128/msphere.00834-21
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Citation: Biofilm bacterial dynamics and changes in inorganic nitrogen density due to the presence of freshwater pearl mussels (2022, April 26) retrieved 26 June 2022 from https://phys.org/news/2022-04-biofilm-bacterial-dynamics-inorganic-nitrogen.html
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