Effects of engineered silver nanoparticles on the growth and activity of ecologically important microbes

<jats:title>Summary</jats:title><jats:p>Currently, little is known about the impact of silver nanoparticles (<jats:styled-content style="fixed-case">AgNPs</jats:styled-content>) on ecologically important microorganisms such as ammonia‐oxidizing bacteria (<jats:styled-content style="fixed-case">AOB</jats:styled-content>). We performed a multi‐analytical approach to demonstrate the effects of uncapped nanosilver (<jats:styled-content style="fixed-case">uAgNP</jats:styled-content>), capped nanosilver (<jats:styled-content style="fixed-case">cAgNP</jats:styled-content>) and <jats:styled-content style="fixed-case">Ag</jats:styled-content><jats:sub>2</jats:sub><jats:styled-content style="fixed-case">SO</jats:styled-content><jats:sub>4</jats:sub> on the activities of the <jats:styled-content style="fixed-case">AOB</jats:styled-content>: <jats:styled-content style="fixed-case"><jats:italic>N</jats:italic></jats:styled-content><jats:italic>itrosomonas europaea</jats:italic>, <jats:styled-content style="fixed-case"><jats:italic>N</jats:italic></jats:styled-content><jats:italic>itrosospira multiformis</jats:italic> and <jats:styled-content style="fixed-case"><jats:italic>N</jats:italic></jats:styled-content><jats:italic>itrosococcus oceani</jats:italic>, and the growth of <jats:styled-content style="fixed-case"><jats:italic>E</jats:italic></jats:styled-content><jats:italic>scherichia coli</jats:italic> and <jats:styled-content style="fixed-case"><jats:italic>B</jats:italic></jats:styled-content><jats:italic>acillus subtilis</jats:italic> as model bacterial systems in relation to <jats:styled-content style="fixed-case">AgNP</jats:styled-content> type and concentration. All <jats:styled-content style="fixed-case">Ag</jats:styled-content> treatments caused significant inhibition to the nitrification potential rates (<jats:styled-content style="fixed-case">NPRs</jats:styled-content>) of <jats:styled-content style="fixed-case"><jats:italic>N</jats:italic></jats:styled-content><jats:italic>itrosomonas europaea</jats:italic> (decreased from 34 to &lt; 16.7 <jats:styled-content style="fixed-case">μM</jats:styled-content> <jats:styled-content style="fixed-case">NH</jats:styled-content><jats:sub>4</jats:sub><jats:sup>+</jats:sup> oxidized day<jats:sup>−1</jats:sup>), <jats:styled-content style="fixed-case"><jats:italic>N</jats:italic></jats:styled-content><jats:italic>itrosospira multiformis</jats:italic> (decreased from 46 to &lt; 24.8 <jats:styled-content style="fixed-case">μM</jats:styled-content> <jats:styled-content style="fixed-case">NH</jats:styled-content><jats:sub>4</jats:sub><jats:sup>+</jats:sup> oxidized day<jats:sup>−1</jats:sup>) and <jats:styled-content style="fixed-case"><jats:italic>N</jats:italic></jats:styled-content><jats:italic>itrosococcus oceani</jats:italic> (decreased from 26 to &lt; 18.4 <jats:styled-content style="fixed-case">μM</jats:styled-content> <jats:styled-content style="fixed-case">NH</jats:styled-content><jats:sub>4</jats:sub><jats:sup>+</jats:sup> oxidized day<jats:sup>−1</jats:sup>). <jats:styled-content style="fixed-case"><jats:italic>E</jats:italic></jats:styled-content><jats:italic>scherichia coli</jats:italic>‐<jats:styled-content style="fixed-case">A</jats:styled-content>g interactions revealed that the percentage of damaged <jats:styled-content style="fixed-case"><jats:italic>E</jats:italic></jats:styled-content><jats:italic>. coli</jats:italic> cells was 45% greater with <jats:styled-content style="fixed-case">Ag</jats:styled-content><jats:sub>2</jats:sub><jats:styled-content style="fixed-case">SO</jats:styled-content><jats:sub>4</jats:sub>, 39% with <jats:styled-content style="fixed-case">cAgNPs</jats:styled-content> and 33% with <jats:styled-content style="fixed-case">uAgNPs</jats:styled-content> compared with controls. Generally, the inhibitory effect on <jats:styled-content style="fixed-case">AOB NPRs</jats:styled-content> and <jats:styled-content style="fixed-case"><jats:italic>E</jats:italic></jats:styled-content><jats:italic>. coli</jats:italic>/<jats:styled-content style="fixed-case"><jats:italic>B</jats:italic></jats:styled-content><jats:italic>. subtilis</jats:italic> growth was in the following order <jats:styled-content style="fixed-case">Ag</jats:styled-content><jats:sub>2</jats:sub><jats:styled-content style="fixed-case">SO</jats:styled-content><jats:sub>4</jats:sub> &gt; <jats:styled-content style="fixed-case">cAgNP</jats:styled-content> &gt; <jats:styled-content style="fixed-case">uAgNP</jats:styled-content>. In conclusion, <jats:styled-content style="fixed-case">AgNPs</jats:styled-content> (especially <jats:styled-content style="fixed-case">cAgNPs</jats:styled-content>) and <jats:styled-content style="fixed-case">Ag</jats:styled-content><jats:sub>2</jats:sub><jats:styled-content style="fixed-case">SO</jats:styled-content><jats:sub>4</jats:sub> adversely affected <jats:styled-content style="fixed-case">AOB</jats:styled-content> activities and thus have the potential to severely impact key microbially driven processes such as nitrification in the environment.</jats:p>