1. Introduction
With the growth of the global population and the massive utilization of
petroleum products, petrochemical production continues to develop,
resulting in marine and land environmental pollution. This can happen
during oil production, transportation, use and leakage (Ramadass et al.,
2018; Baoune et al., 2019). Due to the complex composition, high
biological toxicity, and low bioavailability of petroleum hydrocarbons,
they are harmful to soil, groundwater, and the regional ecological
environment (Dariush et al., 2007, Hassan and AI-Jawhari 2014).
Moreover, the oil site soil is often accompanied by salinization, which
makes its remediation extremely difficult.
The soil microbiota plays a vital role in the material cycles and energy
flow in the soil system, such as the biogeochemical cycle of nitrogen,
carbon and phosphorus (Liu et al., 2020). Furthermore, when soil is
disturbed by pollutants, soil microorganisms react immediately to resist
the invasion of pollutants. Many studies have used DNA-based technology
to study the microbiota in petroleum hydrocarbons or organic pollutants
polluted soil, water, and sediments (Sheng et al., 2016, Zhou et al.,
2020, Hamdan and Salam 2020). As an oil-polluted lake in France, the
profiles of the sedimentary bacterial community have been associated
with the oil-contaminated gradient (Paisse et al., 2018). The complex
pollution composition exerts selective pressure on these bacterial
communities, and the oil degrading bacteria do not increase with the
increase of oil pollutants. On the contrary, the study on the microbial
community of an oil contaminated site in China found that there were
more oil-degrading microorganisms in polluted soils than in clean soils
(Liu et al., 2019). However, few studies concentrated on the effects of
oil contamination on soil microbial community in the long or short term,
and few studies focused on culture-dependent microorganisms.
Microorganisms do not exist alone in the soil, but form a complex matrix
of ecological interaction. With the exception of the environmental
factors, community interactions also affect microbial behavior,
including the interaction between prokaryotes and eukaryotes. The
coexistence of bacteria and fungi in the same environment inevitably
leads to material and energy exchange among them (De Boer et al., 2005;
Benoit et al., 2015; Warmink et al., 2009). Further studies have been
carried out in natural samples describing the coexistence between
bacterial and fungal communities recently. The network study for
limited-length polymorphism endpoint data showed that bacterial and
fungal communities and soil properties were linked, as shown by a
typical correlation module (De Menezes et al., 2015). The network study
provides richer insights into microbial assemblages compared to simple
indices of heterogeneity and structure. In addition, they supplement an
important facet to our knowledge of the interactions among microbiota or
between a known community and environmental parameters such as soil
contamination. Up to now, though, few networks was assembled for soil
microbial communities under petroleum contamination, especially under
differing pollution duration.
Metals and metalloids are indispensable for agricultural products and
land. In a previous study, Haraguchi (2004) described for the first time
the “metallomic” as an “integrated biometal science,” trying to
supply a systematic perception of the absorption, change, function, and
excretion of the metal within biological systems. Metallomics
concentrates on a systematic investigation of metallomes and the
interactions and functional associations of metals or metalloid species
with gene, protein, metabolite, and other biomolecule in cells (Ge and
Sun 2009). The examination of metals obtained from soil—the
metallomes—can be detected through inductively coupled plasma–mass
spectrometry (ICP–MS). Meanwhile, a previous work has shown that the
shift of the soil ionome resulting from different fertilization can
drive the assembly of the soil microbiome and alter microbial
interaction and function (Liu et al., 2020). However, to date, little is
known about how the soil metallome reacts to oil contamination in the
long- or short-term.
To explore the short-term and long-term impacts of petroleum pollution
on soil, the physicochemical properties, the contents of 18 metals, the
diversity, composition, and structure of soil microbial communities were
determined. In addition, three strains of bacteria with high petroleum
degradation efficiency were isolated from long-term
petroleum-contaminated soil, and the degradation efficiency of their
synthetic community on petroleum hydrocarbons and the growth of maize
seedlings under oil pollution stress were explored. We hypothesized
that: 1) Petroleum pollution in different years caused significant
differences in the diversity and composition of soil microbial
community. 2) Petroleum pollution with different years will
significantly change the topological parameters of the soil microbial
network.