Soil microorganisms play an essential role in soil ecosystem
processes such as organic matter decomposition, nutrient
cycling, and plant nutrient availability. The land use for greenhouse
cultivation has been increasing continuously, which
involves an intensive input of agricultural materials to enhance
productivity; however, relatively little is known about
bacterial communities in greenhouse soils. To assess the effects
of environmental factors on the soil bacterial diversity
and community composition, a total of 187 greenhouse soil
samples collected across Korea were subjected to bacterial
16S rRNA gene pyrosequencing analysis. A total of 11,865
operational taxonomic units at a 97% similarity cutoff level
were detected from 847,560 sequences. Among nine soil factors
evaluated; pH, electrical conductivity (EC), exchangeable
cations (Ca2+, Mg2+, Na+, and K+), available P2O5, organic
matter, and NO3-N, soil pH was most strongly correlated
with bacterial richness (polynomial regression, pH: R2 =
0.1683, P < 0.001) and diversity (pH: R2 = 0.1765, P < 0.001).
Community dissimilarities (Bray-Curtis distance) were positively
correlated with Euclidean distance for pH and EC
(Mantel test, pH: r = 0.2672, P < 0.001; EC: r = 0.1473, P < 0.001). Among dominant phyla (> 1%), the relative abundances
of Proteobacteria, Gemmatimonadetes, Acidobacteria,
Bacteroidetes, Chloroflexi, and Planctomycetes were also more
strongly correlated with pH and EC values, compared with
other soil cation contents, such as Ca2+, Mg2+, Na+, and K+.
Our results suggest that, despite the heterogeneity of various
environmental variables, the bacterial communities of
the intensively cultivated greenhouse soils were particularly
influenced by soil pH and EC. These findings therefore shed
light on the soil microbial ecology of greenhouse cultivation,
which should be helpful for devising effective management
strategies to enhance soil microbial diversity and improving
crop productivity.