Figure 2 Most abundant bacterial classes and genera in tomato fruit surface GSK126 molecular weight samples (2008 and 2009). A) Bacterial classes in surface selleck products and groundwater treated fruit surfaces, indicating a predominance of Gammaproteobacteria in both years. B) Bacterial genera in surface and groundwater treated fruit surfaces. Diversity analysis using operational taxonomic units To compute estimates of species-level diversity and perform comparisons between environments, all sequences were clustered into operational taxonomic units (OTUs) using Mothur [30] and a similarity threshold of 95% (see Methods). The total number of unique OTUs within each environment was 494

(pg), 399 (ps), 228 (wg) and 1342 (ws). After computing rarefaction curves for each sample (Figure 3A), we immediately observed that the surface water samples were significantly more diverse than the others, and that groundwater and fruit surface samples are indistinguishable in terms of diversity. Additionally, the Shannon diversity index and Chao1 estimator were calculated for selleck chemicals each sample, and again we see that the ws samples are the most diverse at the OTU level (Figure 3B). Figure 3 OTU-based bacterial diversity analysis of water and crop samples. (A) Rarefaction curves displaying the average number of OTUs discovered by random sampling

within each sample. We observe a higher diversity in all surface water samples (ws) relative to fruit surface and groundwater samples. (B) This increased diversity is also apparent through the Chao1 and Shannon diversity estimators. To avoid bias due to different sampling depths, we first rarefied the data by randomly selecting 1100 sequences from each sample. Note that Chao1 estimates for total species-level diversity in surface water samples consistently exceed 1000 species, while all other environments fall below 500. To assess the diversity captured with the samples, we calculated the Good’s Coverage Estimator

on the OTUs from each sample using TCL Mothur. Results indicated that we captured between 93 and 98% of the species in all of the samples except for ws samples, where we only identified between 70 and 73% of the species. We then examined shared OTUs between individual replicates and treatments. Fruit surface environments shared approximately half their OTUs, and these represented more than 90% of the sequences in both samples. In contrast, water environments shared only 31 OTUs, which represented 2% of the OTUs present in surface water and 14% of those in groundwater. These shared OTUs corresponded to 62% of the sequences in groundwater, but only 6% of the sequences in surface water. These results again point to the greater differences between water-based microbial communities as compared to those in the treated tomato fruit surfaces.