Species diversity of bacteria isolated from soil, sludge sewage and digestate

Abstract

Background and aim. Scientific research confirms the positive aspects of the using sludge to improve the physical, chemical and biological properties of soil. Organic compounds are well absorbed by plants, and thus the value of their organic matter increases. The one of the main difficulties in the management of sewage sludge or digestate are bacteria, which may cause humans’ infections The aim of the study was to species identification of bacteria from the Enterobacteriaceae family and chosen Gram-positive bacteria presented in soil, sewage sludge and digestate. Methods. Identification of bacteria isolated from arable soil (82), sewage sludges (9) and digestate (9) samples was based on biochemical (ENTEROtest 24N, NEFERMtest 24N, GEN III MicroLog M System) and genetic methods. Total DNA from bacterial cultures was isolated using Qiamp® DNA Mini Kit. PCR reaction was performed with primers complementary to the conserved ribosomal DNA regions of most bacterial species, including the 16S rRNA genes. Sequencing was performed on ABI Prism 310 Genetic Analyzer (Applied Biosystems, USA). Results. From the soil samples, Gram-negative bacteria belonging to the genus Serratia, Citrobacter and Enterobacter were identified most frequently. The other identified bacteria species were: Pantoea agglomerans, Escherichia vulneris, E. coli, Hafnia alvei, Aeromonas salmonicida, A. hydrophila, Kluyvera intermedia, Rahnella aquatilis, Raoultella terrigena, Buttiauxella gaviniae, Klebsiella pneumoniae. Bacteria isolated from the sewage sludges and digestate included: Yersinia intermedia, Y. enterolitica, Y. frederiksenii, E. coli, Enterobacter cloacae, Klebsiella oxytoca, K. pneumoniae, Morganella morganii, Aeromonas salmonicida, Proteus mirabilis. Salmonella johannesburg and Listeria monocytogenes have been found in one and in 2 samples, respectively. Conclusions. Standards relating to the use of sewage sludge and digestate for fertilization in agriculture should take into pathogenic/potentially pathogenic bacterial species presented in organic additives. Keywords: Bacteria species, Enterobacteriaceae, soil, sewage sludge, digestate. Funding: The research was financed by NCBiR (Poland); Project No.: GOSPOSTRATEG-III/0061/2020-00.