This Week In Biofilms And Microbiomes: Monday March 28, 2016

A round-up of what we read last week in the media's coverage of biofilms and microbiomes research.

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A new study, published in the ISME (International Society for Microbial Ecology) Journal, has given smokers another reason to quit the habit: smoking alters bacterial balance in the mouth, potentially leading to shifts in functional pathways with implications for smoking-related diseases. Researchers from NYU Langone Medical Center, assessed the relationship of cigarette smoking with the oral microbiome using 16S rRNA gene sequencing on mouthwash DNA samples from 1,204 US adults (112 smokers, 571 former smokers, and 521 nonsmokers). Sequences were clustered into operational taxonomic units (OTUs) using QIIME and metagenomic content was inferred using PICRUSt. The investigators found that overall oral microbiome composition differed between current and non-current (former and never) smokers. More than 150 bacterial species showed significantly increased growth in the mouths of smokers, while another 70 showed sharp decreases in growth. For instance, smokers had relatively fewer species of Proteobacteria (at 4.6 percent of overall bacteria in the mouth), than nonsmokers (at 11.7 percent), with Proteobacteria shown to be involved in the breakdown of toxic chemicals introduced by smoking. By contrast, smokers had 10 percent more species of Streptococcus than nonsmokers, with Streptococcus known to promote tooth decay. The team also found that the oral microbiome of smokers bounces back after they quit smoking, with all former smokers (who had not smoked for at least 10 years) showing the same microbial balance as nonsmokers. This is the first study to report phylum- and class-wide associations of bacterial taxa with smoking status; the robust findings may relate to the large sample size, which provided the power to detect these associations. "Further experiments will be needed, however, to prove that these changes weaken the body's defenses against cancer-causing chemicals in tobacco smoke, or trigger other diseases in the mouth, lungs, or gut," says Jiyoung Ahn, an associate professor at NYU Langone and associate director of population sciences at its Laura and Isaac Perlmutter Cancer Center. Read the coverage by EurekAlert, Science Daily and PR Newswire.

A recent study, published in mBio, suggests that microbial biofilms are far more resistant when they arise from clumps than when they form from separate, individual cells. The popular notion about development of a biofilm involves attachment of single planktonic bacterial cells to a surface and the subsequent development of a mature biofilm. However, a new study conducted by researchers at the University of Copenhagen, indicates that this view of bacteria needs to be revised. The team used a combination of experimental and computational approaches to determine the relative fitness of single cells and preformed aggregates during early development of Pseudomonas aeruginosa biofilms, and found that the relative fitness of aggregates depends markedly on the density of surrounding single cells, i.e., the level of competition for growth resources. When competition between aggregates and single cells is low, an aggregate has a growth disadvantage because the aggregate interior has poor access to growth resources. However, if competition is high, aggregates exhibit higher fitness, because extending vertically above the surface gives cells at the top of aggregates better access to growth resources. These findings show that an aggregate landing on a surface will eventually outcompete the biofilm population arising from single cells attached around the aggregate and dominate the local biofilm development. This implies that we need to change the way we think about microbial infections in the body, 60-80% of which are caused by bacteria growing as a biofilm rather than as free-floating or single cells, and is therefore more resilient toward antibiotics and immune response. The press release was covered by

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Richa Dandona

Partnerships and Operations Manager, Nature Partner Journals, Nature Research