Unraveling the ecological processes modulating the population structure of Escherichia coli in a highly polluted urban stream network.

Escherichia coli dynamics in urban watersheds are affected by a complex balance among external inputs, niche modulation and genetic variability. To explore the ecological processes influencing E. coli spatial patterns, we analyzed its abundance and phylogenetic structure in water samples from a stream network with heterogeneous urban infrastructure and environmental conditions. Our results showed that environmental and infrastructure variables, such as macrophyte coverage, DIN and sewerage density, mostly explained E. coli abundance. Moreover, main generalist phylogroups A and B1 were found in high proportion, which, together with an observed negative relationship between E. coli abundance and phylogroup diversity, suggests that their dominance might be due to competitive exclusion. Lower frequency phylogroups were associated with sites of higher ecological disturbance, mainly involving simplified habitats, higher drainage infrastructure and septic tank density. In addition to the strong negative relationship between phylogroup diversity and dominance, the occurrence of these phylogroups would be associated with increased facilitated dispersal. Nutrients also contributed to explaining phylogroup distribution. Our study proposes the differential contribution of distinct ecological processes to the patterns of E. coli in an urban watershed, which is useful for the monitoring and management of fecal pollution.

Aerobic methanotrophs in an urban water cycle system: Community structure and network interaction pattern.

Aerobic methane-oxidizing bacteria (MOB) play an important role in reducing methane emissions in nature. Most current researches focus on the natural habitats (e.g., lakes, reservoirs, wetlands, paddy fields, etc.). However, methanotrophs and the methane-oxidizing process remain essentially unclear in artificial habitat, such as the urban water cycle systems. Here, high-throughput sequencing and qPCR were used to analyze the community structure and abundance of MOB. Six different systems were selected from Yunyang City, Chongqing, China, including the raw water system (RW), the water supply pipe network system (SP), the wastewater pipe network system (WP), the hospital wastewater treatment system (HP), the municipal wastewater treatment plant system (WT) and the downstream river system (ST) of a wastewater treatment plant. Results clearly showed that the MOB community structure and network interaction patterns of the urban water cycle system were different from those of natural water bodies. Type I MOB was the dominant clade in HP. Methylocysis in Type II was the most abundant genus among the whole urban water cycle system, indicating that this genus had a high adaptability to the environment. Temperature, dissolved oxygen, pH and concentration significantly affected the MOB communities in the urban water cycle system. The network of MOB in WT was the most complicated, and there were competitive relationships among species in WP. The structure of the network in HP was unstable, and therefore, it was vulnerable to environmental disturbances. Methylocystis (Type II) and Methylomonas (Type I) were the most important keystone species in the entire urban water cycle system. Overall, these findings broaden the understanding of the distribution and interaction patterns of MOB communities in an urban water cycle system and provide valuable clues for ecosystem restoration and environmental management.

Impaired dendritic cell differentiation of CD16-positive monocytes in tuberculosis: role of p38 MAPK.

Tuberculosis (TB) is one of the world's most pernicious diseases mainly due to immune evasion strategies displayed by its causative agent Mycobacterium tuberculosis (Mtb). Blood monocytes (Mos) represent an important source of DCs during chronic infections; consequently, the alteration of their differentiation constitutes an escape mechanism leading to mycobacterial persistence. We evaluated whether the CD16(+)/CD16(-) Mo ratio could be associated with the impaired Mo differentiation into DCs found in TB patients. The phenotype and ability to stimulate Mtb-specific memory clones DCs from isolated Mo subsets were assessed. We found that CD16(-) Mos differentiated into CD1a(+) DC-SIGN(high) cells achieving an efficient recall response, while CD16(+) Mos differentiated into a CD1a(-) DC-SIGN(low) population characterized by a poor mycobacterial Ag-presenting capacity. The high and sustained phosphorylated p38 expression observed in CD16(+) Mos was involved in the altered DC profile given that its blockage restored DC phenotype and its activation impaired CD16(-) Mo differentiation. Furthermore, depletion of CD16(+) Mos indeed improved the differentiation of Mos from TB patients toward CD1a(+) DC-SIGN(high) DCs. Therefore, Mos from TB patients are less prone to differentiate into DCs due to their increased proportion of CD16(+) Mos, suggesting that during Mtb infection Mo subsets may have different fates after entering the lungs.

Differential induction of macrophage cell death by antigens of a clustered and a non-clustered multidrug-resistant Mycobacterium tuberculosis strain from Haarlem family.

Some multidrug-resistant (MDR) Mycobacterium tuberculosis (Mtb) genotypes are the cause of large outbreaks, including strain M identified in Argentina. In contrast, its kin strain 410 has only caused a single case to date. Cell wall antigens from Mtb were associated with the modulation of macrophage (MΦ) cell death, and the ability to inhibit of MΦ apoptosis is considered a virulence mechanism. In this study, the ability these two clinical isolates with divergent epidemiology to induce MΦ cell death was evaluated using whole inactivated bacteria. We showed that gamma-irradiated (I-) strains induced MΦ necrosis, the strongest inducer being I-410. Cell death biased towards apoptosis with the heat-killed (hk) strains, both hk-MDR strains being poorer inducers of MΦ apoptosis than was H37Rv. These effects were partly due to their ability to induce anti-apoptotic mechanisms which were not related to the lack of tumor necrosis factor alpha induction or a compensatory effect of interleukin-10. The most noticeable difference between strain M and strain 410 was the ability shown by hk-M to interfere with apoptosis induced by hk-H37Rv. Thus, heat-stable and heat-labile antigens from these epidemiologically divergent Mtb strains differ in their ability to manipulate MΦ death.

Paradoxical role of CD16+CCR2+CCR5+ monocytes in tuberculosis: efficient APC in pleural effusion but also mark disease severity in blood.

The role of CD16(-) and CD16(+) Mo subsets in human TB remains unknown. Our aim was to characterize Mo subsets from TB patients and to assess whether the inflammatory milieu from TB pleurisy modulate their phenotype and recruitment. We found an expansion of peripheral CD16(+) Mo that correlated with disease severity and with TNF-α plasma levels. Circulating Mo from TB patients are activated, showing a higher CD14, CD16, and CD11b expression and Mtb binding than HS. Both subsets coexpressed CCR2/CCR5, showing a potential ability to migrate to the inflammatory site. In tuberculous PF, the CD16(+) subset was the main Mo/MΦ population, accumulation that can be favored by the induction of CD16 expression in CD16(-) Mo triggered by soluble factors found in this inflammatory milieu. CD16(+) Mo in PF were characterized by a high density of receptors for Mtb recognition (DC-SIGN, MR, CD11b) and for lipid-antigens presentation (CD1b), allowing them to induce a successful, specific T cell proliferation response. Hence, in tuberculous PF, CD16(+) Mo constitute the main APC population; whereas in PB, their predominance is associated with the severity of pulmonary TB, suggesting a paradoxical role of the CD16(+) Mo subset that depends on the cellular localization.

A functional misexpression screen uncovers a role for enabled in progressive neurodegeneration.

Drosophila is a well-established model to study the molecular basis of neurodegenerative diseases. We carried out a misexpression screen to identify genes involved in neurodegeneration examining locomotor behavior in young and aged flies. We hypothesized that a progressive loss of rhythmic activity could reveal novel genes involved in neurodegenerative mechanisms. One of the interesting candidates showing progressive arrhythmicity has reduced enabled (ena) levels. ena down-regulation gave rise to progressive vacuolization in specific regions of the adult brain. Abnormal staining of pre-synaptic markers such as cystein string protein (CSP) suggest that axonal transport could underlie the neurodegeneration observed in the mutant. Reduced ena levels correlated with increased apoptosis, which could be rescued in the presence of p35, a general Caspase inhibitor. Thus, this mutant recapitulates two important features of human neurodegenerative diseases, i.e., vulnerability of certain neuronal populations and progressive degeneration, offering a unique scenario in which to unravel the specific mechanisms in an easily tractable organism.