Effective methods for extracting extracellular polymeric substances from Shewanella oneidensis MR-1

Abstract

Extracellular polymeric substances (EPS) play crucial roles in bio-aggregate formation and survival of bacterial cells. To develop an effective but harmless method for EPS extraction from Shewanella oneidensis MR-1, five extraction methods, i.e. centrifugation (control), heating (40, 45, 50, and 60 °C), and treatments with HSO, ethylenediaminetetraacetic acid (EDTA) and NaOH, were examined, respectively. Results from scanning electron microscope and flow cytometric analyses indicate that MR-1 cells were severely broken by HSO, NaOH and heating temperature ≥45 °C. Proteins and polysaccharides in EPS extracted by heating at 40 °C were 7.12 and 1.60 mg g dry cell, respectively. Although EDTA treatment had a relatively lower yield of EPS (proteins and polysaccharides yields of 5.15 and 1.30 mg g dry cell, respectively), cell lysis was barely found after EPS extraction. Three peaks were identified from the three-dimensional excitation-emission matrix spectrum of each EPS sample, suggesting the presence of protein-like substances. Furthermore, the peak intensity was in good accordance with protein concentration measured by the chemical analysis. In short, heating (40 °C) and EDTA treatments were found the most suitable methods for EPS extraction considering the cell lysis and EPS content, composition and functional groups together.

Extracellular polymeric substances are transient media for microbial extracellular electron transfer

“…As a widely studied electrochemically active strain ( 2 , 8 ), MR-1 was first chosen as the main target to address the role of EPS in EET. The strain was cultured statically in Luria-Bertani broth at 30°C for 48 hours to harvest mature cells and obtain more EPS, and a heat treatment was used to remove EPS ( 20 ).…”

“…Heat treatment can remove EPS by enhancing the molecular, protein, and membrane dynamics, and hence accelerating the EPS dissolution in extract solution ( 13 ), and our previous study has shown that heat treatment is an efficient method for EPS extraction ( 20 ). The cells were harvested by centrifugation (5000 g , 10 min, 4°C) and washed twice with 0.9% NaCl (w/v) solution.…”

Impact of reactive surfaces on the abiotic reaction between nitrite and ferrous iron and associated nitrogen and oxygen isotope dynamics

“…It is known to perform dissimilatory metal reduction by utilizing alternative terminal electron acceptors such as elemental sulfur, Mn(IV), Fe(III), or NO − 3 . As S. oneidensis produces large amounts of EPS (Dai et al, 2016;Heidelberg et al, 2002) but is not capable of oxidizing Fe(II) (Lies et al, 2005;Piepenbrock et al, 2011), i.e. there is no interference with abiotic reactions involving Fe/chemodenitrification, we chose concentrated and sterilized S. oneidensis for our dead biomass experiments.…”

“…strain BoFeN1, showing that c-cytochromes were present in EPS secreted and could indeed act as electron shuttling agents involved in electron transfer, thereby supporting chemolithotrophic growth. As S. oneidensis (our model organisms used as DB supply) is known to produce large amounts of EPS, harbouring ccytochromes (Dai et al, 2016;Liu et al, 2012;White et al, 2016), a potential impact of EPS on the reaction between NO − 2 and Fe(II) needs to be considered. However, possible cytochromes present in the EPS most likely lost their activity due to protein denaturation during autoclaving (Liu and Konermann, 2009;Tanford, 1970).…”

The electrically conductive pili of Geobacter soli

“…Assays for extracellular cytochrome content in extracted EPS of biofilm The EPS 423 of biofilms were extracted using a previously modified method (52,53). The biofilm 424 was gently scraped off the graphite plate and dissolved in 3 ml of 0.9% (w/v) NaCl 425 solution.…”