Schulze‐Makuch, Dirk

Motility is a great biosignature and its pattern is characteristic for specific microbes. However, motion does also occur within the cell by the myriads of ongoing processes within the cell and the exchange of gases and nutrients with the outside environment. Here, we propose that the sum of these processes in a microbial cell is equivalent to a pulse in complex organisms and suggest a first approach to measure the “living pulse” in microorganisms. We emphasize that if a “living pulse” can be shown to exist, it would have far-reaching applications, such as for finding life in extreme environments on Earth and in extraterrestrial locations, as well as making sure that life is not present where it should not be, such as during medical procedures and in the food processing industry.

Single-cell sequencing is a powerful technology that provides the capability of analyzing a single cell within a population. This technology is mostly coupled with microfluidic systems for controlled cell manipulation and precise fluid handling to shed light on the genomes of a wide range of cells. So far, single-cell sequencing has been focused mostly on human cells due to the ease of lysing the cells for genome amplification. The major challenges that bacterial species pose to genome amplification from single cells include the rigid bacterial cell walls and the need for an effective lysis protocol compatible with microfluidic platforms. In this work, we present a lysis protocol that can be used to extract genomic DNA from both gram-positive and gram-negative species without interfering with the amplification chemistry. Corynebacterium glutamicum was chosen as a typical gram-positive model and Nostoc sp. as a gram-negative model due to major challenges reported in previous studies. Our protocol is based on thermal and chemical lysis. We consider 80% of single-cell replicates that lead to >5 ng DNA after amplification as successful attempts. The protocol was directly applied to Gloeocapsa sp. and the single cells of the eukaryotic Sphaerocystis sp. and achieved a 100% success rate.

The presence of microbialite structures in a freshwater, dimictic mid-latitudelake and their establishment after the last ice age about 10,000 years ago is puzzling.Freshwater calcite microbialites at Pavilion Lake, British Columbia, Canada, consist of acomplex community of microorganisms that collectively form large, ordered structuredaggregates. This distinctive assemblage of freshwater calcite microbialites was studied through standard microbial methods, morphological observations, phospholipid fatty acid(PLFA) analysis, DNA sequencing and the identification of quorum sensing molecules.Our results suggest that the microbialites may represent a transitional form from theexclusively prokaryotic colonial precursors of stromatolites to the multicellular organismicaggregates that give rise to coral reefs.