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A non-genetic transgenerational inhibitory effect on sexual reproduction has been demonstrated in Brachionus plicatilis in relation to environmental predictability. Indeed, clones of this species from more predictable environments do not respond to sex-inducing cues during several generations after leaving diapause. Notwithstanding, the molecular basis of this effect is still unknown. In this work, the expression level of genes related to the synthesis of sex hormones and to a potential epigenetic signalling mechanism were tracked along successive generations from diapausing eggs in clones of B. plicatilis populations inhabiting ponds with different level of environmental predictability. The selected genes were (1) the 17-β-dehydrogenase gene (edh), involved in the synthesis of 17-β-estradiol hormone in rotifers, and (2) the DNMT2 gene (meth), as a candidate epigenetic mechanism of control. According to expectations, results showed an increasing expression of edh across generations in clones from those the more predictable ponds. This finding provides a putative role of estradiol in the transgenerational effect. However, no differences were found in the meth gene neither across generations nor regarding the environmental predictability. Despite this, we point out alternatives for future research on the inherited gene regulation mechanism behind the transgenerational effect. [ABSTRACT FROM AUTHOR]

Natural water bodies contain physically interconnected habitats suitable for microbes, such as different water layers and substrates for biofilms. Yet, little is known on the extent to which microbial communities are shared between such habitats and whether differences and similarities are consistent between sites. Here we explicitly tested hypotheses on similarities between aquatic bacterial communities found floating in water, in association with daphnids and with copepods, within bottom sediments, and on littoral stones of a lake. Through high-throughput 16S rDNA amplicon sequencing, distinguishable patterns were retrieved between habitats. In particular, community composition was more similar between the two zooplankton taxa, between the two water depths, and was rather different in sediments, where a large fraction of the total diversity was present. Most bacterial taxa were restricted to one or few habitats, whereas only few were found as generalists on different habitats. Our results indicate a limited role of source–sink dynamics between habitats for aquatic bacteria. Similarly to patterns of diversity in larger organisms, community composition was different between habitats, potentially because of specific mechanisms creating and maintaining habitat filtering. [ABSTRACT FROM AUTHOR]

The beta lactamase gene blaCTX-M, responsible of the resistance to cephalosporins, has been detected in microbes from hospitals to open waters. We studied the seasonality and stability of blaCTX-M in Lake Maggiore over 3 years and the role of potential inputs of allochthonous bacteria and/or antibiotic pollution in promoting its occurrence. blaCTX-M was mainly present from January to July in the pelagic microbial community and the gene occurrence was significantly related to low water temperature. To evaluate its temporal stability in the bacterial community over a short period, we measured blaCTX-M daily over the course of 6 days. The gene was below the limit of quantification except for one sampling when its abundance peaked, suggesting a point contamination. The bacterial community of the lake in which blaCTX-M was detected suggests that at least two distinct bacterial populations contained the gene. The occurrence of known blaCTX-M containing genera and the occurrence of the gene, however, did not overlap. Furthermore, the experimental addition of cefotaxime to lake water incubations did not promote abundance of the gene. These data imply that blaCTX-M was present in the environmental microbial community. Increases of gene abundances were likely caused by environmental parameters other than antibiotic contamination. [ABSTRACT FROM AUTHOR]