Megan Dixon’s paper, Time of arrival during plant disease progression and humidity additively influence Salmonella enterica colonization of lettuce, was published in Applied and Environmental Microbiology today. This study is the first to examine the role of relative humidity in the interplay between plant disease caused by Xanthomonas vitians and the enteric pathogen, S. enterica, colonization of the apoplast. Megan found that there is a “window of opportunity” during bacterial spot disease progression that favors S. enterica entering the apoplast and replicating in this protected niche. If S. enterica arrives to early plant defenses activated at early infection by host detection of the plant pathogen curtails S. enterica colonization success. If S. enterica arrives too late, the human pathogen fails to reach the apoplast, likely due to deterioration of the leaf from the ravaging effects of disease. Megan also determined that S. enterica can benefit from X. vitians catabolization of sucrose. In the plant, S. enterica is at a disadvantage for growth with sucrose as the most abundant sugar, our data suggest that S. enterica can replicate in the presence of X. vitians actively growing in a medium with sucrose as the sole carbon source. These results suggest that one of the benefits to S. enterica to colonization of a X. vitians-infected host is available nutrients lacking in a healthy lettuce host.

Megan summarized her findings in another useful cartoon, seen below.

Congratulations Megan and her team of undergraduate researchers – Dharshita and Sonia.