Evaluation of the effects of various culture conditions on Cr(VI) reduction by Shewanella oneidensis MR‐1 in a novel high‐throughput mini‐bioreactor

Abstract

1The growth and Cr(VI) reduction by Shewanella oneidensis MR-1 was examined using a 2 mini-bioreactor system that independently monitors and controls pH, dissolved oxygen, and 3 temperature for each of its 24, 10-mL reactors. Independent monitoring and control of each 4 reactor in the cassette allows the exploration of a matrix of environmental conditions known to 5 influence S. oneidensis chromium reduction. S. oneidensis MR-1 grew in minimal medium 6 without amino acid or vitamin supplementation under aerobic conditions but required serine and 7 glycine supplementation under anaerobic conditions. Growth was inhibited by dissolved oxygen 8 concentrations >80%. Lactate transformation to acetate was enhanced by low concentration of 9 dissolved oxygen during the logarithmic growth phase. Between 11 and 35°C, the growth rate 10 obeyed the Arrhenius reaction rate-temperature relationship, with a maximum growth rate 11 occurring at 35°C. S. oneidensis MR-1 was able to grow over a wide range of pH (6-9). At 12 neutral pH and temperatures ranging from 30-35°C, S. oneidensis MR-1 reduced 100 µM Cr(VI) 13 to Cr(III) within 20 minutes in the exponential growth phase, and the growth rate was not 14 affected by the addition of chromate; it reduced chromate even faster at temperatures between 35 15 and 39°C. At low temperatures (<25°C), acidic (pH<6.5), or alkaline (pH>8.5) conditions, 100 16 µM Cr(VI) strongly inhibited growth and chromate reduction. The mini-bioreactor system 17 enabled the rapid determination of these parameters reproducibly and easily by performing very 18 few experiments. Besides its use for examining parameters of interest to environmental 19 remediation, the device will also allow one to quickly assess parameters for optimal production 20 of recombinant proteins or secondary metabolites 21

Anaerobic Central Metabolic Pathways in Shewanella oneidensis MR-1 Reinterpreted in the Light of Isotopic Metabolite Labeling

“…S. oneidensis strain MR-1 was purchased from the American Type Culture Collection (ATCC 700550) and stored at Ϫ80°C prior to use. All cultures used a previously reported minimal medium (34) 2 O, and 0.08 mg Na 2 WO 4 · 2H 2 O). The medium was supplemented with ϳ20 mM 1-13 C-labeled sodium L-lactate (99%; Cambridge Isotope) as the carbon source and 30 mM TMAO (98% pure; Sigma) or 23 mM fumarate (99% pure; Sigma) as the electron acceptor.…”

“…Over the last few decades, Shewanella spp. have been used in bioremediation applications involving a variety of toxic metals (21,23,26,34,36,38). Recently, researchers also found that the versatile respiration ability of S. oneidensis MR-1 may be used to generate electricity from many substrates under anaerobic conditions (15)(16)(17)(18)28).…”

“…Although the tricarboxylic acid (TCA) cycle is often observed to be incomplete in many other anaerobes (absence of 2-oxoglutarate dehydrogenase activity), isotopic labeling supports the existence of a complete TCA cycle in S. oneidensis MR-1 under certain anaerobic conditions, e.g., TMAO-reducing conditions. Shewanella oneidensis MR-1, formerly called Shewanella putrefaciens MR-1 or Alteromonas putrefaciens MR-1, is able to utilize many carbon sources, including lactate, acetate, pyruvate, and some amino acids (13,21,23,26,34,36,38). It can reduce a variety of electron acceptors besides oxygen, including Fe(III), Mn(IV), trimethylamine N-oxide (TMAO), dimethyl sulfoxide, sulfur, nitrate, and fumarate (29,32,36).…”

Modeling Substrate Utilization, Metabolite Production, and Uranium Immobilization in Shewanella oneidensis Biofilms

“…In this research, we focus on its ability to reduce and immobilize uranium (U), an important contaminant because of its prevalence in the environment and toxicity to many organisms, including humans. Since the biotransformation of metals and radionuclides (e.g., during uranium bioremediation) can impact cellular metabolism (Viamajala et al, 2002(Viamajala et al, , 2004Tang et al, 2006), it is important to investigate experimentally and theoretically using mathematical models, and understand these changes in order to improve bioremediation techniques and applications.…”

“…Previously, the growth kinetics of S. oneidensis under various conditions were investigated using planktonic cultures (Myers and Nealson, 1988;Liu et al, 2005;Tang et al, 2006). A kinetic model was developed to predict substrate utilization, metabolite production, and cell growth using planktonic cultures under varied O 2 concentrations (Tang et al, 2007b).…”