Highlights d Cities possess a consistent ''core'' set of non-human microbes d Urban microbiomes echo important features of cities and city-life d Antimicrobial resistance genes are widespread in cities d Cities contain many novel bacterial and viral species

The dynamic response of organisms exposed to environmental pathogens determines their survival or demise, and the outcome of this interaction depends on the host’s susceptibility and pathogen-dependent virulence factors. The transmission of acquired information about the nature of a pathogen to progeny may ensure effective defensive strategies for the progeny’s survival in adverse environments. Environmental RNA interference (RNAi) is a systemic and heritable mechanism and has recently been linked to antibacterial and antifungal defenses in both plants and animals. Here, we report that the second generation of Caenorhabditis elegans living on pathogenic bacteria can avoid bacterial infection by entering diapause in an RNAi pathway-dependent mechanism. Furthermore, we demonstrate that the information encoding this survival strategy is transgenerationally transmitted to the progeny via the maternal germ line.

Inorganic polyphosphate (polyP) plays a significant role in increasing bacterial cell resistance to unfavorable environmental conditions and in regulating different biochemical processes. Using transmission electron microscopy of the polychlorinated biphenyl (PCB)-degrading bacterium Pseudomonas sp. strain B4 grown in defined medium with biphenyl as the sole carbon source, we observed large and abundant electron-dense granules at all stages of growth and following a shift from glucose to biphenyl or chlorobiphenyls. Using energy dispersive X-ray analysis and electron energy loss spectroscopy with an integrated energy-filtered transmission electron microscope, we demonstrated that these granules were mainly composed of phosphate. Using sensitive enzymatic methods to quantify cellular polyP, we confirmed that this polymer accumulates in PCB-degrading bacteria when they grow in the presence of biphenyl and chlorobiphenyls. Concomitant increases in the levels of the general stress protein GroEl and reactive oxygen species were also observed in chlorobiphenyl-grown cells, indicating that these bacteria adjust their physiology with a stress response when they are confronted with compounds that serve as carbon and energy sources and at the same time are chemical stressors.Polyphosphate (polyP) is a ubiquitous linear polymer consisting of hundreds of orthophosphate residues (P i ) linked by high-energy phosphoanhydride bonds. The best-known enzymes involved in the metabolism of polyP in bacteria are the polyphosphate kinase (PPK) that catalyzes the reversible conversion of the terminal phosphate of ATP into polyP and the exopolyphosphatase that processively hydrolyzes the terminal residues of polyP to liberate P i (15).The involvement of polyP in the regulation of both enzyme activities and expression of large group of genes is the basis of survival for different bacteria, including pathogens, under stress conditions and of adaptation to the stationary growth phase (reviewed in reference 16). Mutant bacterial cells that lack polyP survive poorly during growth in the stationary phase and are less resistant to heat, oxidants, osmotic challenge, antibiotics, and UV radiation (6,13,24,25,35). polyP accumulation in response to nutrient deprivation has also been reported in the genus Pseudomonas, and recent studies have demonstrated that PPK is essential in Pseudomonas aeruginosa not only for various forms of motility (26, 27) but also for biofilm development, quorum sensing, production of virulence factors, and virulence in the burned-mouse pathogenesis model (28).Chlorinated biphenyls (CBs) and polychlorinated biphenyls (PCBs) belong to one of the most widely distributed classes of chlorinated chemicals in the environment (33, 34). The toxicities and carcinogenicities of some PCB congeners make them a serious environmental and health problem (14). For cleanup of large areas of PCB-contaminated soils and aquatic environments bioremediation seems to be a promising approach (22). Although many genetic, enzymological, and bioch...

No abstract