Lectura 1 - 07 Octubre 2014

Expressing Horizontally Acquired Genes Requires Multitasking

Before taking advantage of foreign genes, bacterial recipients need to overcome their own gene-silencing mechanisms

Irina Artsimovitch

Frequent exchanges of horizontally transferred (HT) DNA shape the evolution of microorganisms, a process affecting an estimated 75% of bacterial genes. Some of those HT genes, particularly those encoding virulence and antibiotic resistance and carried on DNA islands, present a formidable threat to humankind.

Lectura - 23 Septiembre de 2014

Omic Approaches in Microbial Ecology: Charting the Unknown 

Analysis of whole-community sequence data is unveiling the diversity and function of specific microbial groups within uncultured phyla and across entire microbial ecosystems

Brett J. Baker and Gregory J. Dick

Nearly a decade ago, Jill Banfıeld of the University of California, Berkeley, and her collaborators applied random shotgun DNA sequencing to microbial biofılms from extremely acidic waters in the Iron Mountain mine in California, assembling genomes for the most abundant of those microbes. Although they relied on Sanger sequencing, whose yields are modest compared to other DNA-sequencing techniques that are now available, their efforts showed that genome sequences could be reconstructed directly from environmental samples, bypassing cultivation while providing insights into the uncultured members of that microbial community.

Lectura 2 - 9 Septiembre 2014

Insights into the phylogeny and coding potential of microbial dark matter

Christian Rinke, Patrick Schwientek, Alexander Sczyrba, et al.

Microorganisms are themost diverse and abundant cellular life forms on Earth, occupying every possible metabolic niche. The large majority of these organisms have not been obtained in pure culture and we have only recently become aware of their presence mainly through cultivation-independent molecular surveys based on conservedmarker genes (chiefly small subunit ribosomal RNA; SSU rRNA) or through shotgun sequencing (metagenomics). As an increasing number of environments are deeply sequenced using next-generation technologies, diversity estimates for Bacteria and Archaea continue to rise, with the number of microbial ‘species’ predicted to reach well into the millions.

Lectura 1 - 9 Septiembre 2014

Bypassing Cultivation To Identify Bacterial Species

Culture-independent genomic approaches identify credibly distinct clusters,avoid cultivation bias, and provide true insights into microbial species

Luis M. Rodriguez-R and Konstantinos T. Konstantinidis

Whether bacterial species exist as a natural unit remains an unresolved issue, one with important practical challenges, including that of correctly identifying microorganisms and diagnosing the causative agents of microbial diseases. The current bacterial species defınition is based on genetic and phenotypic distinctiveness of organisms grouped under the same name.

Lectura 2 - 2 Septiembre 2014

Making Great Cheeses, Part 2
During affinage, microorganisms gradually ripen cheese to its fully mature state—a process that can take weeks or years

Paul S. Kindstedt

The fırst day of cheese making establishes its chemical composition. During affınage, or fınishing, the unaged cheese is transformed or “ripened” to its fully mature state. Finishing depends on the cheese maker, or affıneur, subjecting the cheese to specifıc environmental conditions and physical manipulations over weeks, months, or even years depending on variety. However, no cheese can mature to greatness unless it begins with the right chemical composition. Here we explore the microbiological, chemical, and environmental conditions during cheese ripening, with well-known cheese varieties as examples.

Lectura 1 - 2 Septiembre 2014

The Making of Great Cheeses
The first steps in making great cheeses involve building the right physical and chemical environment to support microbial ripening

Paul S. Kindstedt

Cheese making transforms milk into either fresh or ripened cheese, with the aging process ranging from weeks to years. The fırst days establish the chemical characteristics of the cheese before it begins to age, setting the stage for microbial ripening. Of the plethora of organisms in new cheese, some remain viable and may proliferate during aging, others will be suppressed, while still others may be suppressed initially and then favored or vice versa, depending on the chemical environment to which they are subject.

Lectura 2 - 26 Agosto 2014

Cycling Single-Carbon Compounds: from Omics to Novel Concepts
Formerly obscure microbial species emerge as major players in environmental cycling of carbon and nitrogen

Ludmila Chistoserdova, Marina G. Kalyuzhnaya, and Mary E. Lidstrom

We study the bacteria that oxidize methane and potentially other single-carbon compounds in Lake Washington in Seattle. These organisms typically are found in the top layers of the sediment, where they capture the methane that forms following methanogenic degradation of organic matter in the anoxic layers of the sediment, or where they consume other similar single-carbon compounds.

Lectura 1 - 26 Agosto 2014

Bacterial Vesicles in the Ocean

David Scanlan

Biological production of extracellular vesicles is widespread, with vesicles produced by species across all three branches of the tree of life ( 7). In Gram-negative bacteria, vesicles are produced when small regions of the outer membrane bulge away from the cell before pinching off and being released. Biller et al. carefully purifi ed 70 to 100 nmsized membrane-bound extracellular vesicles from exponentially growing Prochlorococcus cells.

Lectura 2 - 19 de Agosto 2014

Life: is it inevitable or just a fluke?
Nick Lake

 Life arose only once on Earth, and if a sample of one were all we had to go on, no grand conclusions could be drawn. But there is more than that. Look at a vital ingredient for life - energy - suggests that simple life is common throughout the universe, but it does nos inevitably evolve into more complex forms such as animals. I might be wrong, but if I'm right, the immense delay between life first appearing on Earth ad the emergence of complex life points to another, very different explanation for why we have yet to discover aliens...

Mundane or marvel? (Image: Aires

photography/Getty Images)

Lectura 1 - 19 de Agosto 2014

New Look at Ancient Mineral Could Scrap a Test for Early Oxygen

Richard A. Kerr

Geologists trying to sniff out signs of oxygen in Earth’s early air have long struggled with a major obstacle: eons-old rocks that provide only a ragged, fragmentary record of the gas. Even so, some have for decades taken the presence of the mineral hematite in a so-called banded iron formation (BIF) in northwestern Australia as a sign that 2.5 billion years ago, Earth’s atmosphere had at least a trace of oxygen. The ruddy mineral was thought to record the moment when photo synthesis fi rst pushed oxygen to levels high enough to fully oxidize iron...