Department of Molecular Biology, Genetic Engineering and Biotechnology Research Institute, University of Sadat City, Sādāt, Egypt.
Botany and Microbiology Department, Faculty of Science, Menoufia University, Menoufia, Egypt.
Curr Microbiol. 2022 Aug 22;79(10):294. doi: 10.1007/s00284-022-02981-8.
Haloalkophilic bacteria have a potential advantage as a bioremediation organism of high oil-polluted and industrial wastewater. In the current study, Haloalkaliphilic isolates were obtained from Hamralake, Wadi EL-Natrun, Egypt. The phenotype script, biochemical characters, and sequence analysis of bacterial-16S rRNA were used to identify the bacterial isolates; Halomonas HA1 and Marinobacter HA2. These strains required high concentrations of NaCl to ensure bacterial growth, especially Halomonas HA1 strain. Notably, both isolates can degrade phenol at optimal pH values, between 8 and 9, with the ability to grow in pH levels up to 11, like what was seen in the Halomonas HA1 strain. Moreover, both isolates represent two different mechanistic pathways for phenol degradation. Halomonas HA1 exploits the 1,2 phenol meta-cleavage pathway, while Marinobacter HA2 uses the 2,3 ortho-cleavage pathway as indicated by universal primers for 1,2 and 2,3 CTD genes. Interestingly, Marinobacter HA2 isolate eliminated the added phenol within an incubation period of 72 h, while the Halomonas HA1 isolate invested 96 h in degrading 84% of the same amount of phenol. Phylogenetic analysis of these 1,2 CTD (catechol dioxygenase) sequences clearly showed an evolutionary relationship between 1,2 dioxygenases of both Halomonadaceae and Pseudomonadaceae. In comparison, 2,3 CTD of Marinobacter HA2 shared the main domains of the closely related species. Furthermore, semi-quantitative RT-PCR analysis proved the constitutive expression pattern of both dioxygenase genes. These findings provide new isolates of Halomonas sp. and Marinobacter sp. that can degrade phenol at high salt and pH conditions via two independent mechanisms.
嗜盐碱性细菌作为高污染石油和工业废水的生物修复生物具有潜在优势。在本研究中，从埃及瓦迪纳特伦的哈罗拉雷克获得了嗜盐碱性分离物。使用表型脚本、生化特性和细菌 16S rRNA 序列分析来鉴定细菌分离物；盐单胞菌 HA1 和海洋杆菌 HA2。这些菌株需要高浓度的 NaCl 才能确保细菌生长，尤其是盐单胞菌 HA1 菌株。值得注意的是，这两种分离物都可以在最佳 pH 值 8 到 9 之间降解苯酚，并能够在高达 pH 值 11 的水平下生长，就像盐单胞菌 HA1 菌株一样。此外，这两种分离物都代表了苯酚降解的两种不同机制途径。盐单胞菌 HA1 利用 1,2 苯酚间位裂解途径，而海洋杆菌 HA2 使用 2,3 邻位裂解途径，如 1,2 和 2,3 CTD 基因的通用引物所示。有趣的是，海洋杆菌 HA2 分离株在 72 小时的孵育期内消除了添加的苯酚，而盐单胞菌 HA1 分离株则用 96 小时降解了相同数量的苯酚的 84%。这些 1,2 CTD（儿茶酚双加氧酶）序列的系统发育分析清楚地显示了 Halomonadaceae 和 Pseudomonadaceae 两种 1,2 加氧酶之间的进化关系。相比之下，海洋杆菌 HA2 的 2,3 CTD 共享密切相关物种的主要结构域。此外，半定量 RT-PCR 分析证明了两种加氧酶基因的组成型表达模式。这些发现为盐单胞菌和海洋杆菌属的新分离株提供了依据，它们可以通过两种独立的机制在高盐和 pH 条件下降解苯酚。
