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By Rachel Adams
Well, I have always told people that we need more mixing of art and science. In recent years we have seen lots of attempts to do some sort of art inspired by - or even incorporating - microbes. But this is perhaps the other side of the coin.
You could say that I'm milking this one study design - one in which we surveyed the airborne microbial communities and surfaces around different units of a university housing complex - and you'd be right. But for good reason: it's a powerful study design. We have replication of residential units of a common design across buildings; we took simultaneous outdoor and indoor samples; and the samples collected aerosols in a non-invasive way over a discrete, one-month time period.
We've published previously on the airborne fungi and the fungi on surfaces, and now our analysis of the airborne bacteria has just been published.
We found that bacterial bioaerosols were influenced by which unit the sample came from and the room type in which it was sampled. On the other hand, our earlier study showed that fungal bioaerosols showed influence of season, unit, and to a small extent, the room in which the dust was collected.
This is one of the first published studies that consider fungi and bacteria from the same samples, and it suggests that the processes the influence these two microorganisms have some commonalities but key differences. In common, both the composition of fungi and bacteria in samples decrease as the samples move farther away in space - the distance-decay effect. In contrast, there is an abundance of human-associated bacteria indoors, and this isn't matched with fungi. There were many human-associated bacterial that were abundant indoors, and rare or absent outdoors. Fungal taxa that were abundant indoors were also abundant outdoors.
Lest you worry, we've used up many of our samples, so there will be no more publications from this one study. Bacteria on households surfaces have been tackled already, anyway (here and here). As with most studies, it will be interesting to compare these results to other studies in the pipeline that further characterize the microbes - both bacteria and fungi - in homes.
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by Holly Ganz
We've been hearing a lot about Microbes in Space. But what about Microbes in Smog? Here in California, we know a thing or two about smog. To avoid it during the drought, we have been having a lot of Spare the Air Days lately to try to protect our air quality and reduce the amount of particulate matter in the air. Indeed small particulates have been linked to asthma, respiratory disease, emphysema, lung cancer. With more than 20 million people living in Beijing, air quality has declined dramatically. You can find daily air quality forecasts for Beijing here and you can follow Beijing air quality on Twitter @BeijingAir. Poor air quality has become such a problem in Beijing that in 2013 tourism dropped significantly compared to 2012. In a recent article, Cao et al. 2014 (sorry! paywall) used metagenomics to examine what microbes were found in smog before, during and after a massive, severe smog event that occurred from January 10-14, 2013 in Beijing. At the height of the smog event, particulate matter (PM) 2.5 measured 20 times higher than the WHO guideline value. They collected samples at a air quality monitoring site based at Tsinghua University, an area without nearby pollution sources. Particulate matter was separated by size into ≤ 2.5 um and ≤ 10 um. In all samples, Cao et al. detected 1315 bacterial and archaeal species; most species were terrestrial or fecal in origin and are harmless. A genus containing nitrogen fixing, filamentous bacteria, Frankia was the most abundant genus and the soil bacterium, Geodermatophilus obscurus was also abundant. Several species increased dramatically during the smog event. Thermobifida fusca, a bacterial degrader found in decaying organic matter, showed a five-fold increase. The cause of community-acquired pneumonia, Streptococcus pneumonia showed a two-fold increase. A major fungal allergen, Aspergillus fumigatus increased by about four-fold. Human adenovirus also increased. It's unclear that these microbes are of as much concern to our health as the particulates themselves. Still most research on air quality focuses on particulates and neglects microbes. Researchers in the built environment are also starting to look at microbes in air, including this study by Robertson et al. 2013 that looked at bacteria in bioaerosols in the New York City subway. We know that human babies born through vaginal birth are colonized by their mother's microbes but what about the case of premature infants?
Premature infants are heavily treated with antibiotics and this study found that after the administration of antibiotics, infant guts are colonized by NICU bacterial reservoirs, particularly those found on the feeding and breathing tubes. The study also found a large host of antibiotic-resistance genes in the reconstructed genomes of the gut colonizers.
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