3.4 Soil Microbial community composition
In the whole data set, 1947305 bacterial sequences and 2631038 fungal
sequences obtained from 30 soil samples were classified as 17295 and
1681 ASVs, respectively. On average, 98.11% of the sequences in each
sample were classified as bacteria and only 1.89% were classified as
archaea. For bacteria, Proteobacteria accounted for the highest
proportion among the 30 samples, accounting for 77.79% of the total on
average. Other dominant bacteria include Bacteroidetes (5.02%),
Actinobacteria (3.95%), Firmicutes (3.04%), and Gemmatimonadetes
(2.15%). Among the fungal sequence, the average is 100% fungi.
Ascomycota predominated these samples, accounting for an average of
82.58% of the total sequence. The other prevalent phyla were
Mortierellomycota (10.61%) and Basidiomycota (1.88%).
At the phylum level (Fig. 5 ), compared with the control, the
relative abundance of Proteobacteria were increased, and that of
Gemmatimonadetes and Bacteroidetes were decreased. In the fungal
community, the relative abundance of Ascomycota and Chytridiomycota
increased. In contrast, the relative abundances of Basidiomycota,
Mortierellomycota, and Zoopagomycota decreased after short-term
petroleum contamination (p <0.05) compared with Control. After
long-term petroleum pollution, the relative abundance of Ascomycota was
raised, while that of Chytridiomycota and Zoopagomycota were decreased
(p <0.05).
Among the top 20 identified bacterial genera (Fig. 5 ),Ralstonia , Pseudomonas , Sulfurimonas ,Oleibacter , and Marinobacter were most bounteous. Compared
with Control, relative abundances of Ralstonia ,Acinetobacter , Lysobacter , Kaistobacter ,Stenotrophomonas , Bacillus , Lactobacillus , andSphingomonas were significantly decreased in PS samples.
Conversely, relative abundances of Pseudomonas ,Sulfurimonas , Oleibacter , Marinobacter ,Marinobacterium , Arcobacter , Halomonas ,Pseudidiomarina , and Shewanella were increased (p
<0.05); Relative abundances of Ralstonia ,Marinobacter , Acinetobacter , Lysinibacillus , andLactobacillus were significantly decreased in OS samples,
conversely, relative abundances of Oleibacter ,Alcanivorax , Sediminibacter , Thiobacillus ,Nitrosopumilus , and Candidatus _Portiera were
increased (p <0.05). For fungi, Fusarium ,Mortierella , Pseudallescheria , Alternaria andOchroconis were most abundant. Compared with Control, relative
abundances of Mortierella , Alternaria ,Cladosporium , Syncephalis were decreased in PS samples.
Conversely, relative abundances of Fusarium , Ochroconis ,
and Nigrospora were increased (p <0.05); Relative
abundances of Mortierella , Alternaria ,Cladosporium , Syncephalis , and Aspergillus were
decreased in OS samples, whereas that of Fusarium andOchroconis were increased (p <0.05).