Labtimes 2017-06

page 10 Lab Times 6-2017 Opinion Research Letter from:… France Life’s Gutter Soup By our corresponding author, Cani Veaux W hat is it about the romantic waterways of Paris? Who can forget “The Singing Penis” discovered floating there by researchers from the Musée d’Histoire Na- turelle? They claimed that the remarkably dynamic playing of the water boatman’s penis made it (i.e. a pygmy aquatic in- sect) the “loudest animal on earth” ( PLoS ONE 6(6): e21089; LT 7-2011, p.14). Now, we learn that not only can the sex-life on Parisian wa- terways be very loud, it can also be extremely productive, gen- erating new urban life. In his report on “Aquatic urban ecology at the scale of a capital”, Pascal Jean Lopez claims to be the first to reveal the unsuspected biodiversity of “street gutter-associ- ated eukaryotes” across the entire French capital ( ISME J . 2017 Oct 13. doi: 10.1038/ismej.2017.166. [Epub ahead of print]). Lopez says, he suspected there might be new life in the Pa- risian gutters when he observed the colour of some of the pud- dles at his feet and saw gas bubbles rising to the surface. To in- vestigate the microorganisms they harboured, he analysed dif- ferent samples of non-potable water from the Seine, the Ourcq Canal, curbside water outlets (for street cleaning) and street gutters. Lopez explains the com- plex (if not so romantic) opera- tions of the gutter-washing sys- tem in Paris. Non-potable water is pumped from three stations (two drawing water from the Seine, the third from the Ourcq Canal). This water is stored in seven reservoirs before being dis- tributed to flow along the street gutter network of the city. Toothbrushing gutter mats Sampling of the street gutters was performed in each of Paris’ 20 arrondissements and by random investigation of neighbouring streets for the presence of water “with or without visible biofilms”. Samples from these “gutter mats” – consisting of communities of microorganisms – were collected from a to- tal of 90 street gutters by scrubbing the street surface “using a toothbrush” (possibly one of Lopez’s old ones). Total environ- mental DNA was extracted from each of these samples using a ‘PowerBiofilm DNA Isolation kit’; the subsequent DNA ampli- fication and sequencing yielded ten million raw sequences, as- signable to around 6,900 species of eukaryotic microbes. A large part of this biodiversity consisted of microalgal di- atoms (photoautotrophs) as well as fungi (including some known decomposers), amoebae, Alveolata and Rhizaria, in- cluding parasites, consumers of phototrophs and epibionts that “may regulate the dynamics of gutter mat microbial commu- nities”. Surprisingly, nearly 70% of these species were absent from the sources of the gutter-washing water, while the micro- bial profiles of communities varied greatly between sampling sites. In fact, the street gutters appear to constitute “a unique ecosystem”, in which the microorganisms have adapted to their specific urban environment, street-by-street. Lopez thinks they operate like “tiny roadside treatment plants”, contributing to the decomposition of human waste, street litter and pollutants from motor vehicles, e.g. tyre tread debris, exhaust, motor oil, brake linings and CO 2 . They might even prove to be useful in helping to treat downstream waste- water. But this will require more research. Should, however, his upbeat argument not be enough to get future research funding, Lopez also warns us of the potential dangers – street gutters might facilitate the dispersal of parasites and pathogens with “possible public health consequences”. Therefore, he insists, we definitely need a better understanding of street gutters to help guide “careful planning and targeted action about street clean- ing, and sensitise the public and tourists to the presence of a microalgae life in cities”. Life in cities, death in nature reserves And Lopez is not alone. The field of ur- ban ecology is attracting more and more at- tention, with studies investigating the bio- diversity of built environments, such as of- fices, shopping centres, the surfaces of sub- way systems, urban parks and conservation areas. However, most of these studies have only looked at birds, insects, land plants or prokaryotes. Lopez now hopes his Parisian study will restore some balance in favour of eukaryotic protists. Nevertheless, his enthusiasm for mi- cro-urban ecology as a growth research area stands in stark contrast to the dramatic loss of real ecology in non-urban areas. A recent report revealed a huge decline in flying insects on nature reserves in Germany ( PLoS ONE 12(10):e0185809). Using ‘Malaise traps’ deployed over a period of 27 years in 63 nature protection areas, the Ger- man researchers discovered that the total insect biomass had declined by more than 75% over the course of their survey! This dramatic drop was apparent, regardless of habitat type, and could not be explained by changes in the weather or land use. In fact, they warned that this widespread decline in insect biomass was even more “alarming” when you realised that all their traps were placed within protected areas that are “meant to preserve ecosystem functions and biodiversity”! The implication is that the land surrounding these reserves has become hostile to the insects: pesticides and habitat de- struction are turning farmland into a wildlife desert. So, per- haps Lopez’s study of the urban ecology of microbes adapted to human waste and pollution might also serve to reveal potential new inhabitants for our poisoned landscapes. Public Domain/Olybrius

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