Osmotic response in Leptospirillum ferriphilum isolated from an industrial copper bioleaching environment to sulfate
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2024
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Iron and sulfur-oxidizing microorganisms play important roles in several natural
and industrial processes. Leptospirillum (L.) ferriphilum, is an iron-oxidizing
microorganism with a remarkable adaptability to thrive in extreme acidic
environments, including heap bioleaching processes, acid mine drainage (AMD)
and natural acidic water. A strain of L. ferriphilum (IESL25) was isolated from
an industrial bioleaching process in northern Chile. This strain was challenged
to grow at increasing concentrations of sulfate in order to assess changes in
protein expression profiles, cells shape and to determine potential compatible
solute molecules. The results unveiled changes in three proteins: succinyl CoA
(SCoA) synthetase, isocitrate dehydrogenase (IDH) and aspartate semialdehyde
dehydrogenase (ASD); which were notably overexpressed when the strain grew
at elevated concentrations of sulfate. ASD plays a pivotal role in the synthesis of
the compatible solute ectoine, which was identified along with hydroxyectoine
by using matrix-assisted laser desorption/ionization-time of flight mass
spectrometry (MALDI-TOF). The relationship between IDH, SCoA, and ectoine
production could be due to the TCA cycle, in which both enzymes produce
metabolites that can be utilized as precursors or intermediates in the biosynthesis
of ectoine. In addition, distinct filamentous cellular morphology in L. ferriphilum
IESL25 was observed when growing under sulfate stress conditions. This study
highlights a new insight into the possible cellular responses of L. ferriphilum
under the presence of high sulfate levels, commonly found in bioleaching of
sulfide minerals or AMD environments.