Composted Sewage Sludge Influences the Microbiome and Persistence of Human Pathogens in Soil.

Nikola Major,Smiljana Goreta Ban,Sven Jechalke,Joseph Nesme,Søren J Sørensen,Marko Černe,Jasper Schierstaedt,Adam Schikora,Dean Ban

doi:10.3390/microorganisms8071020

Abstract

Composted sewage sludge (CSS) gained attention as a potential fertilizer in agriculture. Application of CSS increases soil microbial activity and microbial biomass, however, it can also lead to increased chemical and microbiological risks. In this study, we performed microcosm experiments to assess how CSS reshapes the microbial community of diluvial sand (DS) soil. Further, we assessed the potential of CSS to increase the persistence of human pathogens in DS soil and the colonization of Chinese cabbage (Brassica rapa L. subsp. pekinensis (Lour.) Hanelt). The results revealed that CSS substantially altered the prokaryotic community composition. Moreover, addition of CSS increased the persistence of Salmonella enterica serovar Typhimurium strain 14028s and S. enterica serovar Senftenberg in DS soil. However, the enhanced persistence in soil had no impact on the colonization rate of B. rapa grown on soil inoculated with Salmonella. We detected Salmonella in leaves of 1.9% to 3.6% of plants. Addition of CSS had no impact on the plant colonization rate. The use of sewage sludge composts is an interesting option. However, safety measures should be applied in order to avoid contamination of crop plants by human pathogens.

Highlights

Many processes in the soil ecosystem are governed by microorganisms
Taxonomic analysis of the prokaryotic community revealed that the soil communities were composed mostly of 12 bacterial phyla
Proteobacteria, Actinobacteria, Bacteriodetes, Chloroflexi and Verrucomicrobia significantly increased in relative abundance, while Firmicutes, Acidobacteria, Crenarchaeota and Nitrospirae decreased (Table 1) 35 days after transplanting the Brassica rapa (Chinese cabbage) plants

Summary

Introduction

Prominent examples include promotion of plant growth, nutrient cycling and degradation of pollutants [1] These processes are threatened by climate change, changed precipitation patterns and soil degradation due to inappropriate land management practices [2]. By altering the rhizobiome the plant can promote a suppressive soil environment in which the proliferation of a pathogen is inhibited [5]. This may be of great importance since both plant and human pathogenic bacteria can contaminate crop plants and cause yield losses or disease outbreaks [7,8,9]

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Conclusion