Department of Biology, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
Centre for Environmental and Marine Studies, Department of Environment and Planning, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
Sci Total Environ. 2022 Oct 1;841:156677. doi: 10.1016/j.scitotenv.2022.156677. Epub 2022 Jun 13.
Environmental contamination influences the diversity of the resident skin microbial community of amphibians, ultimately affecting the individual's immune system. Wildfires are expected to impact the skin microbiome, since post-fire runoff typically transports hazardous substances, that can affect terrestrial and aquatic ecosystems. The present study is the first to assess the effects of Eucalypt and Pine wildfire ash on cultivable bacterial isolates from the skin microbiome of amphibians, in particular the fire salamander (Salamandra salamandra), a common species in fire-prone Mediterranean ecosystems. To achieve this goal, samples of skin bacteria of adult individuals of S. salamandra were collected at a site without influence of wildfires. The bacterial isolates were tested against the pathogenic agent Aeromonas salmonicida for assessing their antimicrobial activity, before exposing them to a series of dilutions of aqueous extracts of Eucalypt and Pine ashes (AAEs) from high severity wildfires. From the 80 bacterial isolates collected, 48 (mostly Pseudomonas spp.) showed antimicrobial activity. Exposure of bacteria with antimicrobial activity to the Eucalypt and Pine AAEs at concentrations of 0, 6.25, 12.5, 25, 50, 75, and 100%, revealed that bacterial growth could be significantly inhibited, stimulated or unaffected by ash. Growth inhibition was found for Pine and Eucalypt AAEs at concentrations as low as 6.25% and 12.5%, respectively, but were more expressive at concentrations equal or above 50%. Eucalypt AAEs had a higher negative impact on bacterial growth than Pine AAEs, likely due to differences in metal concentrations between ash types. These findings raise concern about the future of amphibians in fire-prone regions since the foreseen increase in fire frequency and severity owing to climate changes are likely to alter the skin microbiome of amphibians, weaken the immune system and consequently increasing the incidence of infections or diseases, further contributing to the decline of the populations.
环境污染会影响两栖动物常驻皮肤微生物群落的多样性，最终影响个体的免疫系统。野火预计会对皮肤微生物群产生影响，因为火灾后的径流通常会携带有害物质，从而影响陆地和水生生态系统。本研究首次评估了桉树和松树野火灰对来自两栖动物皮肤微生物群的可培养细菌分离物的影响，特别是火蜥蜴（Salamandra salamandra），这是火险地中海生态系统中常见的物种。为了实现这一目标，在没有野火影响的地点采集了成年火蜥蜴个体的皮肤细菌样本。在将细菌分离物暴露于一系列桉树和松树灰（AAE）的水溶液稀释度之前，先用致病性气单胞菌（Aeromonas salmonicida）对其进行了抗菌活性测试。从收集的 80 个细菌分离物中，有 48 个（主要是假单胞菌属）显示出抗菌活性。将具有抗菌活性的细菌暴露于桉树和松树 AAE 浓度为 0、6.25、12.5、25、50、75 和 100%，结果表明灰烬可以显著抑制、刺激或不影响细菌的生长。松树和桉树 AAE 浓度低至 6.25%和 12.5%即可抑制细菌生长，但在浓度等于或高于 50%时更为明显。桉树 AAE 对细菌生长的负面影响高于松树 AAE，这可能是由于灰烬中金属浓度的差异所致。这些发现令人担忧火险地区两栖动物的未来，因为气候变化预计会增加火灾的频率和严重程度，这可能会改变两栖动物的皮肤微生物群，削弱免疫系统，从而增加感染或疾病的发病率，进一步导致种群数量下降。
