Niche for high abundant extremophilic microbial communities in an ancient crater

Majed Albokari,Mohammad A A Al-Najjar,Abdulaziz Huraysi,Ibrahim Mashhour

doi:10.1017/s1473550417000295

Abstract

AbstractAl Wahbah Crater, located in a remote area in western Saudi Arabia as part of The Harrat extinct volcanic chain, is 2 km wide with a depth of 250 m. It is registered by the General Commission for Tourism and National Heritage as an ancient and archaeological site. The crater is subjected to extreme environmental conditions as its bottom is rarely subjected to rainfall and mudflows. Because of high temperature, high evaporation rates and extremely limited rainfall, the crater leaves behind dried thick white sodium phosphate crystals. Here, we studied the chemical composition and the microbial community composition using 16S rRNA pyrosequencing in different vertical layers (2, 20, 40, 60, 80 and 100 cm) of the crater sediment. Total sodium concentrations were 28 000– 46 700 ppm and calcium levels were 31 400– 56 500 ppm. In addition, samples were very sulphuric, with sulphate and sulphite levels exceeding 2157 ppm and 5.54 ppm, respectively. Ferric ions concentrations were <0.2 ppm, while nitrate, ammonium and nitrite levels were <2 ppm, 1.5 ppm and 0.05 ppm, respectively. Archaea dominated the surface and the bottom, while bacteria were most common at 20–60 cm. Extremely halophilic archaea and bacteria includingHalorhabdusspp.Halorubrumspp.,Salinibacter iranicusandHalorhodospira halophilawere identified in all samples. Moreover, the relative abundance ofHalanaerobiaceaeaccounted for 22% of the species in the top of the crater.S. iranicusand species belonging toHalorhabdusandHalorubrumthat were identified between 60 and 100 cm could be considered as extreme organisms.

Highlights

Many studies have investigated species compositions in soils of extreme environments (Bontognali et al 2010, 2012; Farías et al 2014; Jay et al 2014); most of these have focused on the top layers or subsurface of soils from areas such as hypersaline sediments and Sabkhas (Kjeldsen et al 2007; Abdeljabbar et al 2013; Al-Najjar et al 2014), or saline/soda lakes (Sorokin et al 2014)
The extremely halophilic bacterium Limimonas halophila was isolated from the mud of hypersaline Lake Aran-Bidgol in Iran (Amoozegar et al 2013), while Salinibacter iranicus and Salinibacter luteus were isolated from Aran-Bidgol salt lake in Iran (Makhdoumi-Kakhki et al 2012)
The bacterial and archaeal communities associated with soil in an ancient, inactive and remote crater in Saudi Arabia, Al Wahbah, were investigated in the upper 100 cm

Summary

Introduction

Many studies have investigated species compositions in soils of extreme environments (Bontognali et al 2010, 2012; Farías et al 2014; Jay et al 2014); most of these have focused on the top layers or subsurface of soils from areas such as hypersaline sediments and Sabkhas (Kjeldsen et al 2007; Abdeljabbar et al 2013; Al-Najjar et al 2014), or saline/soda lakes (Sorokin et al 2014) In such environments, the biogeochemical cycle of nitrogen and sulphur is very important and shapes the microbial communities (Oren 2008; Al-Thani et al 2014). Fluid samples collected from the volcano mud field of Salse di Nirano, Northern Apennines, Italy contained species typical of other saline sediments as well as the sulphate reducers, Clostridium thiosulfatireducens and Desulfovibrio psychrotolerans, which were involved in cycling of sulphur compounds (Kokoschka et al 2015)

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