Redox Sensing within the Genus Shewanella

Abstract

A novel bacterial behavior called congregation was recently described in Shewanella oneidensis MR-1 as the accumulation of cells around insoluble electron acceptors (IEA). It is the result of a series of “run-and-reversal” events enabled by modulation of swimming speed and direction. The model proposed that the swimming cells constantly sense their surroundings with specialized outer membrane cytochromes capable of extracellular electron transport (EET). Up to this point, neither the congregation nor attachment behavior have been studied in any other strains. In this study, the wild type of S. oneidensis MR-1 and several deletion mutants as well as eight other Shewanella strains (Shewanella putrefaciens CN32, S. sp. ANA-3, S. sp. W3-18-1, Shewanella amazonensis SB2B, Shewanella loihica PV-4, Shewanella denitrificans OS217, Shewanella baltica OS155, and Shewanella frigidimarina NCIMB400) were screened for the ability to congregate. To monitor congregation and attachment, specialized cell-tracking techniques, as well as a novel cell accumulation after photo-bleaching (CAAP) confocal microscopy technique were utilized in this study. We found a strong correlation between the ability of strain MR-1 to accumulate on mineral surface and the presence of key EET genes such as mtrBC/omcA (SO_1778, SO_1776, and SO_1779) and gene coding for methyl-accepting protein (MCPs) with Ca+ channel chemotaxis receptor (Cache) domain (SO_2240). These EET and taxis genes were previously identified as essential for characteristic run and reversal swimming around IEA surfaces. CN32, ANA-3, and PV-4 congregated around both Fe(OH)3 and MnO2. Two other Shewanella spp. showed preferences for one oxide over the other: preferences that correlated with the metal content of the environments from which the strains were isolated: e.g., W3-18-1, which was isolated from an iron-rich habitat congregated and attached preferentially to Fe(OH)3, while SB2B, which was isolated from a MnO2-rich environment, preferred MnO2.

Dynamics of Gut Microbiome in Giant Panda Cubs Reveal Transitional Microbes and Pathways in Early Life

“…We found seven important genera that can best discriminate the gut microbial profiles of 0 ~ 1.5-months-old cubs, 1.5 ~ 6-month-old cubs, 6 ~ 9-month-old cubs and adults: Shewanella, Helicobacter, Oblitimonas, Haemophilus, Aeromonas, Listeria , and Fusobacterium . Many species of Shewanella have been reported to reduce metals and toxins (Harris et al, 2017); the other six genera Helicobacter (Fischbach and Malfertheiner, 2018), Oblitimonas (Drobish et al, 2016), Haemophilus (Bakaletz and Novotny, 2018), Aeromonas (Cardoso et al, 2018), Listeria (Salama et al, 2018), and Fusobacterium (Guven and Dizdar, 2018) have been implicated in human diseases. Helicobacter was even expressed in higher abundance in 6 ~ 9-month-old cubs than in adults, suggesting that giant panda would be more susceptible to digestive diseases in this stage.…”

Microbial Nano-Factories: Synthesis and Biomedical Applications

“…Electrons can be moved from reduced organic to oxidized inorganic compounds through microbial dissimilatory anaerobic respiration, thus promoting the formation of crystal/nanoparticles along with bioremediation processes. It is well-documented that the genus Shewanella are able to do the oxidation of organic acids as electron donors and reduction of inorganic metals as electron acceptors (Heidelberg et al, 2002;Harris et al, 2018). Further, the mechanism for detoxifying the immediate cell environment has been developed by microorganisms such as bacteria by reducing toxic metal species into metal nanoparticles (Deplanche and Macaskie, 2008;Murray et al, 2017).…”

Mechanistic Aspects of Microbe-Mediated Nanoparticle Synthesis

“…Electrons can be moved from reduced organic to oxidized inorganic compounds through microbial dissimilatory anaerobic respiration, thus promoting the formation of crystal along with bioremediation processes. It is well documented that the genus Shewanella is able to assist the oxidation of organic acids as electron donors and reduction of inorganic metals as electron acceptors ( Heidelberg et al, 2002 ; Harris et al, 2018 ). Bacterial nanowires and flavins are extracellularly excreted by the genus Shewanella by bioreduction process ( Marsili et al, 2008 ; El-Naggar et al, 2010 ; Beblawy et al, 2018 ).…”