Journal of Microbiology

Journal Article

Identification of trehalose as a compatible solute in different species of acidophilic bacteria: Pedro A. Galleguillos , Barry M. Grail , Kevin B. Hallberg , Cecilia S. Demergasso , D. Barrie Johnson; J. Microbiol. 2018;56(10):727-733. Published online September 28, 2018; DOI: https://doi.org/10.1007/s12275-018-8176-2

Abstract: The major industrial heap bioleaching processes are located in desert regions (mainly Chile and Australia) where fresh water is scarce and the use of resources with low water activity becomes an attractive alternative. However, in spite of the importance of the microbial populations involved in these processes, little is known about their response or adaptation to osmotic stress. In order to investigate the response to osmotic stress in these microorganisms, six species of acidophilic bacteria were grown at elevated osmotic strength in liquid media, and the compatible solutes synthesised were identified using ion chromatography and MALDI-TOF mass spectrometry. Trehalose was identified as one of, or the sole, compatible solute in all species and strains, apart from Acidithiobacillus thiooxidans where glucose and proline levels increased at elevated osmotic potentials. Several other potential compatible solutes were tentatively identified by MALDITOF analysis. The same compatible solutes were produced by these bacteria regardless of the salt used to produce the osmotic stress. The results correlate with data from sequenced genomes which confirm that many chemolithotrophic and heterotrophic acidophiles possess genes for trehalose synthesis. This is the first report to identify and quantify compatible solutes in acidophilic bacteria that have important roles in biomining technologies.

Research Support, Non-U.S. Gov't

Complete Genome of Leptospirillum ferriphilum ML-04 Provides Insight into Its Physiology and Environmental Adaptation: Shuang Mi , Jian Song , Jianqun Lin , Yuanyuan Che , Huajun Zheng , Jianqiang Lin; J. Microbiol. 2011;49(6):890-901. Published online December 28, 2011; DOI: https://doi.org/10.1007/s12275-011-1099-9

Abstract: Leptospirillum ferriphilum has been identified as the dominant, moderately thermophilic, bioleaching microorganism in bioleaching processes. It is an acidic and chemolithoautrophic bacterium that gains electrons from ferrous iron oxidation for energy production and cell growth. Genetic information about this microorganism has been limited until now, which has hindered its further exploration. In this study, the complete genome of L. ferripilum ML-04 is sequenced and annotated. The bacterium has a single circular chromosome of 2,406,157 bp containing 2,471 coding sequences (CDS), 2 rRNA operons, 48 tRNA genes, a large number of mobile genetic elements and 2 genomic islands. In silico analysis shows L. ferriphilum ML-04 fixes carbon through a reductive citric acid (rTCA) cycle, and obtains nitrogen through ammonium assimilation. The genes related to “cell envelope biogenesis, outer membrane” (6.9%) and “DNA replication, recombination and repair” (5.6%) are abundant, and a large number of genes related to heavy metal detoxification, oxidative and acidic stress defense, and signal transduction pathways were detected. The genomic plasticity, plentiful cell envelope components, inorganic element metabolic abilities and stress response mechanisms found the base for this organism’s survival in the bioleaching niche.

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