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Defining the microbial terrain When we consult science in matters of evolution, it points to a common ancestor branching out to different organisms which eventually leads to us, man. Charles Darwin proposed this in his “Origin of the Species�, saying, “There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one�. To add expert views on this subject and the consequences for microbial phylogeny and systematics, FEMS Focus interviewed two authorities in the field, Prof Karl Heinz Schleifer and Prof Milton da Costa. Schleifer has focused on the identification and classification of bacteria since the beginning of his scientific career. He received the FEMSLwoff Award at the 3rd FEMS Congress in Gothenburg, Sweden 2009. Da
Costa, on the other hand, is studying biodiversity in specialized niches such as deep sea brine and is the outgoing President of FEMS. Because of their work, it is possible today to detect and identify bacteria in waste water, food, clinical specimens and environmental samples without first cultivating them in a laboratory – thereby acquiring a whole new insight into the microbial world.
From the Editorial Team With the launch of the first synthetic genome in May this year, it makes one realize how far and even farther science can reach. Indeed, in this discipline, one’s imagination is the only possible limitation. Faced with all this, the innate sentimentality of man suggests looking back and contemplating on how life on Earth arose and how evolution has developed, also generating the current plethora of microbial species. With this in mind, FEMS Focus decided to take a step back and trace the scientific Tree of Life, also known as the Phylogenetic Tree or Evolutionary Tree. This concept relies on the notion that all life on Earth is connected and could have come from a single origin. More than a century ago, it was Charles Darwin himself who claimed that all modern species evolved from a limited set of ancestors, which existed from forefathers of a lesser number. The consequent implications for microbial evolution, phylogeny and systematics are facts that FEMS Focus would like to elucidate. We hope that you will not only join us in this issue, but enjoy it as well. For what’s more interesting than knowing the frontiers of science, but understanding the origin of it all? Tone Tønjum & Chared Verschuur Editors
Haloplasma contractile from a brine-filled deep of the Red Sea. Credits: AndrĂŠ Antunes, Fred Rainey, Robert Huber and Milton da Costa.
Here’s what they have to say about the Phylogenetic Tree of Life: What is the nature of the molecular clock used as a basis for 16S rRNA gene-based phylogeny of bacteria and shaping the Tree of life? Karl Heinz Schleifer (KHS): Small subunit (SSU; 16S/18S) rRNA genes fulfill
all properties of a useful phylogenetic marker. They are present in all living organisms, functionally constant, sufficiently conserved and orthologous markers from acommon ancestor. rRNA genes are rather easy to sequence and align. SSU rRNAs are stable in character, are less subjected to lateral gene transfer than other genes and can be employed for comparative sequence analysis and
subsequent phylogenetic analysis. There is also good agreement between the topology of phylogenetic trees derived from conserved, mostly informational genes (involved in translation or transcription). Moreover, trees inferred from whole genome data are largely consistent with rRNA-derived trees. Milton da Costa (MDC): SSU change slowly over time, with distinct conserved sequences, ena-
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