Introduction
Desert is the largest terrestrial ecosystem on earth, which is sensitive
to human activity and climatic change (Laity, 2009). The common features
of desert, such as extreme drought, strong ultraviolet radiation, and
dramatic temperature fluctuations, limit the survival of plants and
animals in this extreme environment (Sul et al., 2013). Thus,
microorganisms become the dominant component of the desert ecosystem
(Pointing et al., 2012).
The different desert habitats shaped the diverse microorganism
colonization. Cyanobacteria showed the highest abundance in the
biological soil crusts of deserts
(Nagy et al., 2005; Zhang et al.,
2016a; Arocha-Garza et al., 2017; Mogul et al., 2017; Sun et al., 2018).
Actinobacteria was the dominant bacteria in the hyper-arid core in the
Atacama Desert (Crits-Christoph et al., 2013). Many previous studies
focused on the microbial community composition and assembly in the
desert. However, there is no consensus of opinions about which
environment factor is the main driver for the microbial community
assembly on deserts. For example, Zhang et al. (2019) found that
salinity was the key determinant of microbial community assembly in the
Gurbantunggut Desert. Crits-Christoph et al. (2013) emphasized that
water and salt contents were the main factors shaping soil microbiome in
the Atacama Desert. Several previous studies indicated that moisture
influenced the microbial community structures, assembly, and
colonization of the Namib Desert (Warren-Rhodes et al., 2013; Stomeo et
al., 2013; Valverde et al., 2015). Additionally, the results from the
Namib Desert showed that soil chemistry and stochasticity affected the
bacterial community assembly and xeric stress adjusted the variations of
community function (Scola et al., 2018). The inconsistent responses
probably came from the environmental heterogeneity of different deserts.
The Taklimakan Desert is about 1130 kilometers long from east to west,
400 kilometers wide from north to south, covering an area of 337,600
Km2. The terrain is high in the southwest and low in
the northeast, with altitudes ranging from 780 m to 1500 m. The detailed
microbial ecology of the Taklimakan Desert has been poorly investigated
to date. An et al. (2013) investigated the bacterial diversity at the
edge of the Taklimakan Desert. Yu et
al. (2015) isolated 52 ionizing radiation-tolerant bacteria strains from
this desert. Several prior studies identified some novel cultivable
bacteria in the Taklimakan Desert (Zhang et al., 2010; Liu et al., 2010;
An et al., 2010; Liu et al., 2011). Therefore, a comprehensive
investigation is necessary for the taxonomic diversity of bacterial
communities in the Taklimakan Desert.
The
altitudinal gradient is considered a
natural test to evaluate the response of the microbial community to
environmental change (Körner, 2007; Siles and Margesin, 2017). Previous
studies indicated that the altitudinal gradient might lead to different
effects on microbial community population and composition in different
ecosystems (Manzoni et al., 2012; Serna-Chavez et al., 2013). The large
altitude scales might involve different climatic regions, which is
complex to investigate the correlation of microbial community along the
altitudinal gradient (Ren et al., 2018). Thus, it may be easier to
understand the correlation between altitude gradient and microbial
community composition on the same climate conditions. Understanding the
response of altitude gradient to the microbial community was important
for better understanding the adaptability of microorganisms in the
desert ecosystem.
The aims of the present study were to
(1) evaluate the variations of
physicochemical properties and bacterial communities in the sand of the
Taklimakan Desert, (2) reveal how altitude and sand property influence
the structure of bacterial communities, and (3) understand the
specificity and adaptation of bacterial communities in the Taklimakan
Desert.