Despite the large number of scientific studies on the effects of antibiotics on soil microorganisms, little is known about the role played by soil organic matter (humus) in the interaction of ...antibiotics with microorganisms and plants, including the impacts on respiration and growth rate and the implications for nitrogen metabolism, which is an important factor in soil fertility The aim of this study was to analyze the effects of two widely used antibiotics, tetracycline and streptomycin, on microbiotic activity and plant growth in two soils with dissimilar organic carbon content, at the extremes of the fertility spectrum based on humus content. The study used humus-rich (Corg 5.4%) and humus-poor soils (Corg 1.5%) and measured basal respiration, substrate-induced respiration, nitric oxide emission, germination, and growth of white mustard 3 and 60 days after three progressively increasing doses of antibiotics were applied. Tetracycline was found to impair the ecological function of humus-rich soil by reducing denitrification and compromising soil microbial activity, while the effect of streptomycin on humus-poor soil was to reduce nitrification and soil fertility due to nitrogen escape. Both streptomycin and tetracycline increased the microbial biomass and suppressed the growth of white mustard seeds, which indicates an increase in the allelopathic activity of microorganisms in the soil conditions under the influence of antibiotics and their metabolites. Due to the low sorption of streptomycin in humus-poor soils, it poses a great danger to agricultural production, especially in areas of low fertility. In humus-rich soils, high concentrations of tetracycline caused numerous problems, including death of the crop plants. Thus, the effect of antibiotics as well as the more traditional soil pollutants, such as heavy metals, to a large extent, depends on the humus content of soils.
Freshwater Gammarids are common leaf-shredding detritivores, and they usually feed on naturally conditioned organic material, in other words leaf litter that is characterised by an increased ...palatability, due to the action and presence of microorganisms (Chaumot et al. 2015; Cummins 1974: Maltby et al. 2002). Gammarus spp. are biologically omnivorous organisms, so they are involved in shredding leaf litter and are also prone to cannibalism, predation behaviour (Kelly et al. 2002) and coprophagy when juveniles (McCahon and Pascoe 1988). Gammarus spp. is a keystone species (Woodward et al. 2008), and it plays an important role in the decomposition of organic matter (Alonso et al. 2009; Bundschuh et al. 2013) and is also a noteworthy prey for fish and birds (Andrén and Eriksson Wiklund 2013; Blarer and Burkhardt-Holm 2016). Gammarids are considered to be fairly sensitive to different contaminants (Ashauer et al. 2010; Bloor et al. 2005; Felten et al. 2008a; Lahive et al. 2015; Kunz et al. 2010); in fact Amphipods have been reported to be one of the most sensitive orders to metals and organic compounds (Wogram and Liess 2001), which makes them representative test organisms for ecotoxicological studies and valid sentinel species for assessing water quality status (Garcia-Galan et al. 2017).
Identification of people who most frequently engage in sexual risk behaviour while travelling abroad would be useful for the design and targeting of health education and promotion campaigns.
Eligible ...participants were people living in the UK aged 18–34 years who had travelled abroad without a partner in the previous 2 years. Respondents were first screened for eligibility as part of representative face-to-face and telephone surveys by a market research company. Eligible individuals who agreed to take part then underwent a computer-assisted telephone interview. Reinterviewing continued until 400 eligible people had been contacted. We also interviewed a control group of 568 young people who had travelled abroad without a partner in the previous 2 years but who did not report a new sexual relationship during their travels.
One in ten of the eligible participants reported sexual intercourse with a new partner. Travellers who reported a new sexual relationship abroad were also likely to report large numbers of sexual partners at home. Of the 400 people who had a new sexual partner abroad, 300 (75%) used condoms on all occasions with the new partner. Logistic regression modelling showed differences between men and women in those factors linked to the practice of unsafe or safer sex while travelling. For men, patterns of condom use abroad with casual partners (p<0·001) reflected patterns of use at home (p<0·001), whereas for women, patterns of condom use varied according to their partners' backgrounds (p<0·001).
Condoms are widely used among young travellers, but patterns of use vary by sex. Campaigns about sexual health targeted at international travellers should continue, not least because young people who meet new sexual partners abroad may be a convenient proxy group for that minority of the population who report most sexual partners at home. Such campaigns should be designed differently for men and women.
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