Analysis of microbial populations in plastic–soil systems after exposure to high poly(butylene succinate-co-adipate) load using high-resolution molecular technique

Abstract

Background Bio-based and biodegradable plastics are considered as plastics of the future owing to their ability to decompose under various environmental conditions. However, their effects on the soil microbiome are poorly characterised. In this study, we aimed to investigate the effects of an important bio-based and biodegradable plastic, polybutylene succinate-co-adipate (PBSA), on soil microbial diversity and community composition using high-resolution molecular technique (Illumina sequencing) targeting all three microbial domains: archaea, bacteria, and fungi. Results Adding high load of PBSA to soil (6% (w/w)) caused a significant decline in archaeal (13%) and fungal (45%) richness and substantial changes in both bacterial (Proteobacteria, Actinobacteria, and Acidobacteria) and fungal (Eurotiomycetes, Sordariomycetes, Leotiomycetes, and Dothideomycetes) community composition compared with no PBSA addition to soil. The combined effects of PBSA and (NH4)2SO4 fertilisation on the soil microbiome were much greater than the effects of PBSA alone. We only detected opportunistic human pathogens in low abundance on PBSA and in the surrounding soil. However, some plant pathogenic fungi were detected and/or enriched on the PBSA films and in surrounding soil. Apart from plant pathogens, many potential microbial control agents and plant growth-promoting microorganisms were also detected/enriched owing to PBSA addition. Adding high load of PBSA together with (NH4)2SO4 fertilisation can either eliminate some plant pathogens or enrich specific pathogens, especially Fusarium solani, which is economically important. Conclusions We conclude that high load of bio-based and biodegradable PBSA plastic may negatively affect soil microbiome.

Nitrogen fixing bacteria facilitate microbial biodegradation of a bio-based and biodegradable plastic in soils under ambient and future climatic conditions

“…To demonstrate that N fixation is the rate-limiting step in PBSA degradation in soil, we set-up a PBSA laboratory decomposition experiment using the soil from the GCEF experimental plot as described in our previous study. 32 Briefly, PBSA films were treated with 70% ethanol to sterilize their surfaces and cut into pieces (2–5 mm × 2–5 mm). These pieces (1 g or 6% PBSA, w/w) were buried in sterile glass jars containing 15.7 g dry soil equivalent from one of the two following treatments: (i) soil (PBSA-soil; PS treatment) and (ii) soil with N addition (PBSA-soil-N; PSN treatment), with five independent replicates.…”

“…These pieces (1 g or 6% PBSA, w/w) were buried in sterile glass jars containing 15.7 g dry soil equivalent from one of the two following treatments: (i) soil (PBSA-soil; PS treatment) and (ii) soil with N addition (PBSA-soil-N; PSN treatment), with five independent replicates. In the PSN treatment, the soil was supplemented with the same amount of N (1.4 mL of 1.42 M (NH 4 ) 2 SO 4 , equivalent to 0.055 g N per jar or 280 kg N per hectare which is comparable to the highest rate of N fertilisation used in agroecosystems) 32 that is usually present in the initial soil without PBSA. Soils without PBSA (with and without N amendment, 16.7 g) were used as controls.…”

“…PBSA-associated microorganisms were analyzed by scanning electron microscopy (SEM) at 0, 30, and 90 days, and gravimetric mass loss of PBSA as well as microbial community patterns were analyzed after 90 days of incubation using an Illumina MiSeq system with the primer sets described in our previous study (515F/806R for bacteria and fITS7/ITS4 for fungi). 32 The raw bacterial 16S and fungal ITS rRNA gene sequences were deposited in the National Center for Biotechnology Information (NCBI) Sequence Read Archive under the accession number PRJNA702448. All laboratory procedures for Illumina sequencing and SEM were done as previously described.…”

“…All laboratory procedures for Illumina sequencing and SEM were done as previously described. 6,32 Lipase activities in soil were also measured fluorometrically using 4-methylumbelliferone (MUF) at day 90. 33…”

New approaches for the characterization of plastic-associated microbial communities and the discovery of plastic-degrading microorganisms and enzymes

“…Qi et al, found that biodegradable films had a stronger effect on the rhizosphere microbial community than low-density PE (LDPE) and biodegradable films had higher relative abundances of certain bacterial genera including Bacillus , Variovorax and Comamonadaceae [54] . Tanunchai et al, found that adding a biodegradable plastic poly-butylene succinate-co-adipate (PBSA) to soil, microbial communities significantly changed microbial community composition and that archaeal and fungal species richness declined [57] .…”