Recent studies in lactic acid bacteria (LAB) biofilm formation have reported that the functional properties of LAB are associated with biofilm formation. In this study, Pediococcus acidilactici and Lactobacillus plantarum showed the ability to form a biofilm on a solid surface under static conditions. The morphology of LAB on MRS-CR agar showed that both P. acidilactici and L. plantarum could produce exopolysaccharide (EPS) on the cell surface which mainly contributed to forming the biofilm of single and co-culture strains on solid surfaces. Under the flow condition, cell motility played an important role in supporting the cell to overcome the repulsive force to reach and interact with the surface. As a result, the L. plantarum and co-culture cells with higher motility caused a noticeably thicker biofilm on the glass surface compared to the P. acidilactici strain. Moreover, the antagonistic activity assay showed that co-culture biofilm formation improved the antagonistic effects of LAB against Pseudomonas aeruginosa and Salmonella typhimurium compared to those in planktonic culture. It suggested that co-culture biofilm could be an ef fective model to apply useful LAB as potential probiotics and to control pathogen in food chain, especially under the flow condition.
Iron-oxidizing bacterial consortia can be enriched in microbial fuel cells (MFCs) operated with ferrous iron as the sole electron donor. In this study, we investigated the possibility of using such lithotrophic iron-oxidizing MFC (LIO-MFC) systems as biosensors to monitor iron and manganese in water samples. When operated with anolytes containing only ferrous iron as the sole electron donor, the experimented LIO-MFCs generated electrical currents in response to the presence of Fe(2+) in the anolytes. For the concentrations of Fe(2+) in the range of 3-20 mM, a linear correlation between the current and the concentration of Fe(2+) could be achieved (r(2) = 0.98). The LIO-MFCs also responded to the presence of Mn(2+) in the anolytes but only when the Mn(2+) concentration was less than 3 mM. The presence of other metal ions such as Ni(2+) or Pb(2+) in the anolytes reduced the Fe(2+)-associated electricity generation of the LIO-MFCs at various levels. Organic compounds, when present at a non-excessive level together with Fe(2+) in the anolytes, did not affect the generation of electricity, although the compounds might serve as alternative electron donors for the anode bacteria. The performance of the LIO-MFCs was also affected to different degrees by operational parameters, including surrounding temperature, pH of the sample, buffer strength and external resistance. The results proved the potential of LIO-MFCs as biosensors sensing Fe(2+) in water samples with a significant specificity. However, the operation of the system should be in compliance with an optimal procedure to ensure reliable performance.
Geminoarcus maximus sp. nov and Ceramothyrium brevis sp. nov. were isolated from fallen leaves collected from Cuc Phuong, Ninh Binh and Phu Quoc National Park, Viet Nam, respectively. They were described and illustrated. Geminoarcus maximus was similar to the others three known species of Geminoarcus in shape and conidial development, but the sizes of the mature conidia were different from the other species. Ceramothyrium brevis (Stanhughesia morph) has one main axis composed of several cells, 4-8 septate, sometimes have one (rarely two) lateral arm. This characteristic shows similarity with the Stanhughesia carniolica (morph of Ceramothyrium). C. brevis differs from S. carniolica in the size of the conidia. The phylogeny based on D1/D2 of the 28S rDNA gene showed that Geminoarcus is nested in the Trichomeriaceae, Chaetothyriales, Eurotiomycetes. Ceramothyrium brevis is nested in Ceramothyrium spp. clade (Chaetothyriaceae, Chaetothyriales, Eurotiomycetes).
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