Bacterial community composition of bulk soil from date palm (Phoenix dactylifera) farm depend on irrigation water salinity

Non-saline and saline ground water irrigation is extensively used in the arid regions of United Arab Emirates (UAE) for date palm (<em>Phoenix</em> <em>dactylifera</em>) cultivation without knowing its effect on bulk soil bacterial communities. Bulk soil acts as a supply base for microbes and nutrients that are accessed by date palm roots. We collected soil samples from date farms across UAE and performed V3-V4 16s rRNA metabarcoding analysis to understand how bulk soil bacterial diversity and communities respond to irrigation water sources (non-saline and saline groundwater irrigation). There was no significant variation in bulk bacterial diversity (Shannon diversity, richness as well as evenness). But bulk bacterial communities differed between irrigation water sources and irrigation water electrical conductivity was the significant factor that explained a part of community variation. Out of total 5089 OTUs, saline bulk soil harbored only 21.3% of total OTUs compared to 31.5% OTUs in non-saline bulk soil, while 47.15% OTUs shared between both types of irrigation. Proteobacteria abundance was higher in saline bulk soil, while Actinobacteriota abundance was enhanced in non-saline bulk soil. Similar selection was observed at genus level, wherein saline bulk soil showed increase in abundance of <em>Subgroup_10, Nitrospira </em>and<em> Mycobacterium</em>, whereas <em>Microvirga, Ammoniphilus, Nitrospira</em> and <em>Lysinibacillus </em>were elevated in non-saline bulk soil. Saline (<em>Novibacillus</em> and <em>Bauldea</em>) and non-saline bulk soil (<em>Microvirga</em>, <em>Marmoricola</em>, <em>Domibacillus</em>, <em>Oceanobacillus</em>, <em>Bhargavaea</em> and <em>Solirubrobacter</em>) showed significant selection of indicator taxa (P &lt; 0.05). This indicate that bacterial communities colonizing bulk soil differ depending on irrigation water source and it is affected by irrigation water EC.在阿拉伯联合酋长国（United Arab Emirates, UAE）的干旱地区，人们广泛使用非盐渍化与盐渍化地下水开展椰枣（*Phoenix dactylifera*）种植，但此前尚未明确该灌溉方式对原状土壤（bulk soil）细菌群落的影响。原状土壤是椰枣根系可获取的微生物与养分的供应库。研究团队从阿联酋各地的椰枣种植园采集土壤样品，通过V3-V4区16S rRNA 宏条形码（metabarcoding）测序分析，探究原状土壤细菌多样性与群落结构对不同灌溉水源（非盐渍化与盐渍化地下水）的响应规律。研究结果显示，原状土壤的细菌多样性（香农多样性指数、物种丰富度及群落均匀度）未出现显著差异。但不同灌溉水源对应的原状土壤细菌群落结构存在显著差异，灌溉水的电导率（EC）是解释部分群落变异的关键因素。在总计5089个操作分类单元（Operational Taxonomic Unit, OTU）中，盐渍化灌溉对应的原状土壤仅包含总OTU的21.3%，非盐渍化灌溉对应的原状土壤则包含31.5%的OTU，而两类灌溉方式共有的OTU占比为47.15%。变形菌门（Proteobacteria）在盐渍化原状土壤中的相对丰度更高，而放线菌门（Actinobacteriota）在非盐渍化原状土壤中的相对丰度显著提升。属水平上也观察到类似的群落选择现象：盐渍化原状土壤中，*Subgroup_10*、*Nitrospira*（硝化螺旋菌属）与*Mycobacterium*（分枝杆菌属）的相对丰度显著升高；而非盐渍化原状土壤中，*Microvirga*（微枝形杆菌属）、*Ammoniphilus*、*Lysinibacillus*（解赖氨酸芽孢杆菌属）的相对丰度显著提升。此外，盐渍化原状土壤的指示类群（*Novibacillus*（新芽孢杆菌属）与*Bauldea*）以及非盐渍化原状土壤的指示类群（*Microvirga*、*Marmoricola*、*Domibacillus*、*Oceanobacillus*（海洋芽孢杆菌属）、*Bhargavaea*与*Solirubrobacter*）均呈现显著的群落选择效应（P < 0.05）。该研究表明，定植于原状土壤的细菌群落结构会因灌溉水源的不同而产生差异，且该差异受灌溉水的电导率影响。