Lectura 2 - 28 Octubre 2014

The Neolithic revolution of bacterial genomes

Alex Mira, Ravindra Pushker and Francisco Rodríguez-Valera

Before the Neolithic period, human survival was linked to the hunter-gatherer culture and populations were small and scattered. Approximately 10 000 years ago, however, the advent of agriculture and animal husbandry brought the largest social revolution in the history of humankind. Food resources were more abundant and constant, and the human species increased its population size at an extraordinary annual growth rate of 0.1%. From the point of view of bacterial pathogens, humans suddenly became attractive hosts; they concentrated large populations on limited areas, which maximized the chance for transmission between longer-lived carriers. Thus, it is likely that human population growth and expansion during the Neolithic created a selective pressure that favoured pathogens that specialized in human hosts, originating what was probably the first wave of emerging human diseases.

Lectura 1 - 28 Octubre 2014

The Placenta Harbors a Unique Microbiome

Kjersti Aagaard, JunMa, Kathleen M. Antony, Radhika Ganu, Joseph Petrosino, James Versalovic

Characterizing the processes that govern the establishment of human microbial communities is essential for understanding human development and physiology. Studies have shown that neonates demonstrate complex microbial communities in the gut within the first week of life, with dynamic fluctuations in bacterial composition until a relatively mature equilibrium is reached around 1 to 3 years of age. What shapes these earliest microbial communities, and at what point the infant is first exposed to and colonized by its microbiome, remains unclear. In the first week of life, the full-term neonatal gut microbiome is largely colonized by the phyla Actinobacteria (including Bifidobacterium), Proteobacteria, Bacteroides, and, much less, Firmicutes (including the Lactobacillus spp., which dominate the vaginal flora). In contrast, neonates who weigh <1200 g are dominated by both Firmicutes and Tenericutes phyla, with much less dominance of Actinobacteria. These collective observations raise the possibility that the infant may be first seeded in utero by a common shared low abundance source, such as the placenta, and this seedingmay vary by length of gestation.

Lectura 2 - 21 Octubre 2014

Gut Instinct

Do bacteria in the guts of African hunter-gatherers hold the key to a healthier life? An American anthropologist plans to fi nd out

Jop de Vrieze

Jeff Leach hasn’t showered in a month. Living in a small dome tent close to Lake Eyasi in northern Tanzania, he stopped washing one day because he wants to know how that will change the microbial populations in and on his body. Leach is taking daily samples of his own stool and skin, which he carefully stores in a liquid nitrogen tank until they can be shipped to the United States.

Lectura 1 - 21 Octubre 2014

Antibiotics and Collateral Damage

Alison E. Mather

Most people recognize that antimicrobial drugs are becoming increasingly ineffective, due to the rise of antimicrobial resistance (AMR). The incredible adaptability of microbes and the strong and varied selection pressures to which they are exposed compromise our ability to fight infections, and many common procedures (from hip replacements to cancer therapies) carry greater risks.

Lectura 2 - 14 Octubre 2014

Life at the Poles in the Age of Global Warming: Part 2

Predicting how microorganisms are affected by and could influence global warming proves challenging

Helen A. Vrionis, Lyle G. Whyte, and Robert V. Miller

The strength of sunlight at the poles has a profound impact on the nature and stability of microbial niches. The shallow angle at which sunlight strikes the poles spreads energy over a large area, diminishing its heating power at these latitudes while still driving microbial photosynthesis and primary production. Investigators continue to refıne their projections of how global warming will affect microbial communities at the poles and how these communities, in turn, are likely either to promote or temper those warming trends.

Lectura 1 - 14 Octubre 2014

Life at the Poles in the Age of Global Warming: Part 1

In responding to climate change, microorganisms at the North and South Poles could have amarked influence on global gas fluxes

Helen A. Vrionis, Robert V. Miller, and Lyle G. Whyte

Polar temperatures, ranging from 5 to 20°C in the summer to 30 to 50°C in winter, slow biochemical reactions, and lead to freezing and thus trapping of approximately one-third of global soil carbon. How this carbon is sequestered, modifıed, released, and cycled depends on geological, environmental, and microbial factors. Here we present an overview, setting the stage for a subsequent feature in which we will describe how polar microbial communities might mitigate large-scale carbon variations.

Lectura 2 - 07 Octubre 2014

The Lifestyle of Vibrio cholerae Fosters Gene Transfers

Growing on chitinous surfaces helps these bacteria to initiate horizontal gene transfer and, perhaps, to swap pathogenic traits

Melanie Blokesch

Waterborne Vibrio cholerae bacteria cause cholera, a pandemic during the last 50 years across Asia, Africa, and Latin America. Although most infected individuals do not develop severe symptoms, some become violently ill with severe diarrhea, vomiting, and cramps, and the loss of body fluids, if untreated, can lead to shock and death.

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.