Phylogenetic characterization of microbial mats and isolation of Thermus spp. and sulfur-oxidizing bacteria from Icelandic hot springs

Research output: ThesisDoctoral Thesis (compilation)


Until recently, the only way to describe microbial communities was by cultivation. This is a major obstacle because typically only a small fraction of the microbes can be cultivated by standard techniques. However, the use of rRNA and molecular phylogenetic techniques has allowed us to bypass this limitation.

In this thesis, both of these approaches were used to describe the bacterial diversity of a few Icelandic hot springs. One of these hot springs was a sulfide rich hot spring (sulfur-mat), which was of special interest because it had a great biomass above the photosynthetic border. In order to evaluate the abundance and stability of cultivable Thermus spp. as a function of seasonal changes in this hot spring, fifty strains of Thermus were isolated during one and a half-year period. Multilocus enzyme electrophoresis (MEE) was used to identify the Thermus strains and to examine the genetic structure of the population. The majority of the strains were T. oshimai and that population showed temporal variation. Furthermore, estimation of the association index indicated that recombination events were frequent within the population. A similar study of the population structure of the genus Thermus, within and between geothermal areas in Iceland, indicated that there were some geographical variations and some physiological factors like pH that affect the population structure of Thermus in Iceland.

A new sulfur-oxidizing Thermus strain was isolated and characterized from this same hot spring. A new Hydrogenobacter strain that was able to grow on thiosulfate but could not utilize hydrogen was also isolated. These metabolic features were previously unknown for these genera.

An examination of the microbial diversity of the sulfur-mat, a Chloroflexus-mat and a bacterial mat at 88°C by sequencing of SSU rRNA genes obtained by PCR and cloning from the microbial mats, showed that the population structure was quite different in these three ecosystems. Furthermore, the overall diversity of the sulfur-mat and the 88°C mat was lower than in the Chloroflexus-mat, which may be explained by more extreme physiochemical features in the sulfur-mat and the 88°C mat. Although, representatives of novel divisions were found, the majority of the sequences were >95% related to currently known sequences. Comparison of the present results to published data, indicated that there was a relationship between mat type and composition of Aquificales on one hand, and temperature and sulfide concentration on the other hand.


  • Sigurlaug Skirnisdottir
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Industrial Biotechnology


  • Biochemical technology, hot springs, thermophiles, microbial diversity, SSU rRNA, sulfur-oxidizers, Thermus, Biotechnology, Bioteknik, Biochemistry, Biokemi, Metabolism, Biokemisk teknik
Original languageEnglish
Awarding Institution
Supervisors/Assistant supervisor
  • [unknown], [unknown], Supervisor, External person
Award date2001 Jan 22
  • Biotechnology, Lund University
Publication statusPublished - 2001
Publication categoryResearch

Bibliographic note

Defence details Date: 2001-01-22 Time: 13:15 Place: Lund University, lecture hall K:A, Center for Chemistry and Chemical Engineering, Lund, Sweden External reviewer(s) Name: Kiær Ahring, Birgitte Title: Prof Affiliation: Technical University of Denmark --- Article: I. Skirnisdottir S, Hreggvidsson GO, Hjörleifsdottir S, Marteinsson VT, Petursdottir SK, Holst O, and Kristjansson JK. (2000). Influence of sulfide and temperature on species composition and community structure of hot spring microbial mats. Appl Environ Microbiol 66:2835-2841 Article: II. Hjorleifsdottir S, Skirnisdottir S, Hreggvidsson GO, Holst O, and Kristjansson JK. Species composition of cultivated and non-cultivated bacteria from short filaments in an Icelandic hot spring at 88°C. Accepted for publication in Microbial Ecology Article: III. Skirnisdottir S, Hreggvidsson GO, Holst O, and Kristjansson JK. Isolation and characterization of a mixotrophic sulfur-oxidizing Thermus scotoductus. Accepted for publication in Extremophiles Article: IV. Skirnisdottir S, Hreggvidsson GO, Holst O, and Kristjansson JK. A new ecological adaptation to high sulfide by a Hydrogenobacter sp. growing on sulfur compounds but not on hydrogen. Accepted for publication in Microbiological Research Article: V. Hreggvidsson GO, Skirnisdottir S, Smith B, Helgason E, and Kristjansson JK. Population structure of Thermus in Icelandic hot springs by multilocus enzyme electrophoresis analysis. Manuscript Article: VI. Skirnisdottir S, Hreggvidsson GO, Holst O, and Kristjansson JK. Stability of the Thermus population in a sulfide rich hot spring detected by multilocus enzyme electrophoresis. Manuscript