Desulfovibrio desulfuricans AY5 Isolated from a Patient with Autism Spectrum Disorder Binds Iron in Low-Soluble Greigite and Pyrite

Olga V Karnachuk,Vitaly V Kadnikov,Vasily L Panov,Olga P Ikkert,Viacheslav S Zyusman,Andrey V Mardanov,Marat R Avakyan,Mikhail N.Volochaev,Yurii V Knyazev,Nikolai V Ravin

doi:10.3390/microorganisms9122558

Olga V Karnachuk, Vitaly V Kadnikov + Show 8 more

Open Access

https://doi.org/10.3390/microorganisms9122558

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Abstract

The sulphate-reducing bacteria (SRB) of genus Desulfovibrio are a group of prokaryotes associated with autism spectrum disorders (ASD). The connection between the elevated numbers of Desulfovibrio in the gut of children with ASD compared with healthy children remains unresolved. A conceivable consequence of SRB overgrowth in the gut is the conversion of bioavailable iron into low-soluble crystalline iron sulphides, causing iron deficiency in the organism. In this study, we report the draft genome sequence and physiological features of the first cultivable isolate from a patient with ASD, Desulfovibrio desulfuricans strain AY5.The capability of the strain to produce crystalline iron sulphides was studied under different pH conditions. The most notable greigite(Fe3S4) and pyrite (FeS2) formation was revealed at pH 6.0, which suggests that the iron loss due to insoluble sulphide formation may occur in the proximal part of the gastrointestinal tract. Strain AY5 was adapted to grow under nitrogen-limiting conditions by N2 fixation. The urease found in the strain’s genome may play a role in resistance to acidic pH.

Highlights

Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders characterised by deficits in social communications and reciprocal interactions, as well as restrictive and repetitive behaviour
We investigated the impact of a range of pH conditions on iron sulphide production by strain AY5 in a pH-stat bioreactor and batch culture
Apart from the type strain, six genomes of D. desulfuricans are available in the NCBI database

Summary

Introduction

Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders characterised by deficits in social communications and reciprocal interactions, as well as restrictive and repetitive behaviour. Sulphide produced by SRB binds iron in the form of low-soluble sulphides, reducing its bioavailability. SRB, including Desulfovibrio, have an intrinsic capability to bind metals in sulphides due to the formation of a large quantity of hydrogen sulphide in the course of their energy metabolism. The formation of crystalline iron sulphides—pyrite, marcasite, greigite, and mackinawite—in chemically defined media by Desulfovibrio desulfuricans was first reported by Rickard in 1969 [16]. The preliminary experiments in batch culture without pH control showed that strain AY5 could bind iron in the form of crystalline sulphides. We investigated the impact of a range of pH conditions on iron sulphide production by strain AY5 in a pH-stat bioreactor and batch culture. The draft genome sequence of strain AY5 has been obtained to check its taxonomic position and physiological features

Strain AY5 Cultivation and Physiological Tests

Strain AY5 Genome Sequencing

Strain AY5 Genome and Physiological Properties

Low‐Soluble

Discussion