Heat maps for the mean <i>B</i>. <i>pseudomallei</i> occurrence per quadrant for the dry and wet season; mean soil moisture (“0” dry (<4% vsw), “1” moist (4–20% vsw), “2” wet (>20% vsw)), mean pH and mean electrical conductivity EC, i.e. soil salinity (μS/cm).

<p>Heat maps for the mean <i>B</i>. <i>pseudomallei</i> occurrence per quadrant for the dry and wet season; mean soil moisture (“0” dry (<4% vsw), “1” moist (4–20% vsw), “2” wet (>20% vsw)), mean pH and mean electrical conductivity EC, i.e. soil salinity (μS/cm).</p

Microcosm experiment.

<p><i>B</i>. <i>pseudomallei</i> load after 4 weeks inoculated in sand, sandy clay loam or clay with treatments in triplicate consisting of eight different fertilizers (Tables <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0003635#pntd.0003635.t002" target="_blank">2</a> and <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0003635#pntd.0003635.t003" target="_blank">3</a>), a water-only treatment and a control with no change. The y-axes are in log scale (+0.001) and represent the normalized <i>B</i>. <i>pseudomallei</i> load with the ratio of TTS1 copy number over pt7 control plasmid numbers.</p

Microcosm experiment treatments.

<p>Nine treatments used (plus control) which were each applied in triplicate to each soil type. Fertilizers were applied as per manufacturer’s instructions. All treatments were added with the same amount of water. Ingredients are listed based on package labelling. Numbers indicate % w/w.</p><p>* organic matter 61.5%, organic carbon 35.7%</p><p>** water added to increase VSW of soil by 20%</p><p>Microcosm experiment treatments.</p

The experimental field site.

<p>The setup consisted of two plots with six quadrants each (1x1 metre) with type of treatments or control indicated. Soil of two holes per quadrant (different holes for each round) was tested for <i>B</i>. <i>pseudomallei</i> on a quarterly basis approximately. The arrow marks the direction of the water run-off in the wet season. The number indicates the <i>B</i>. <i>pseudomallei</i> occurrence with the subscript number referring to the baseline occurrence before start of treatment (total 2 holes tested per quadrant) followed by the number of <i>B</i>. <i>pseudomallei</i> positive holes during treatment (total 26 holes tested per quadrant for the duration of the experiment).</p

Results of the analysis on the occurrence of <i>B</i>. <i>pseudomallei</i> on the experimental field site.

<p>The odds ratio refers to the ratio of the odds of <i>B</i>. <i>pseudomallei</i> occurring in soil samples taken a year or more into the experiment from the treatment quadrants to the odds of <i>B</i>. <i>pseudomallei</i> occurring in soil samples from the control quadrants.</p

Treatments applied to the experimental field site over three years.

<p>Treatments applied to the experimental field site over three years.</p

Longitudinal occurrence of <i>B</i>. <i>pseudomallei</i> (red line) on the experimental field site.

<p>The vertical blue lines indicate the start and end of the wet seasons. The y axis depicts the <i>B</i>. <i>pseudomallei</i> occurrence at total four holes per duplicate quadrants. The first measure was taken before treatments were applied.</p

<i>B. pseudomallei</i> occurrence and environmental factors.

<p>Multivariable logistic regression analysis of environmental factors contributing to the presence of <i>B. pseudomallei</i> in soil at either undisturbed, disturbed sites or overall. The analysis was clustered for sites and all odds ratios (OR) were statistically significant. All models were specified correctly as tested by a linktest. “IA Clay+Red Brown Soil” refers to interaction between clay and the soil color red brown.</p

Map of rural Darwin.

<p>Map of rural Darwin showing soil sampling sites with red dots indicating <i>B. pseudomallei</i> positive sites in the dry season 2006 and blue dots no detection of <i>B. pseudomallei</i>. Inset shows map of Australia.</p

<i>B. pseudomallei</i> screening results from soil sampling at 30 cm depth.

<p>Site and sample distribution with <i>B. pseudomallei</i> (<i>B.ps</i>) screening results. 809 soil samples were collected in the Darwin rural area in the dry season of 2006 and the following wet and dry season of 2007. 41% and 57% of re-visited sites in the wet season 2007 and dry season 2007 were positive in the previous dry season 2006.</p