Karki Anand B, Marasini Daya, Oakey Clark K, Mar Kaitlin, Fakhr Mohamed K
Department of Biological Science, The University of Tulsa, Tulsa, OK, United States.
Front Microbiol. 2018 Dec 12;9:2951. doi: 10.3389/fmicb.2018.02951. eCollection 2018.
Aerotolerance in the microaerophilic species was previously reported and could increase bacterial survival and transmission in foods during stressful processing and storage conditions. In this study, 167 isolates (76 and 91 ) were screened for aerotolerance; these strains were previously isolated from retail chicken meat, chicken livers, chicken gizzards, turkey, pork, and beef liver samples. Bacterial cultures were incubated aerobically in Mueller Hinton broth with agitation and viable cell counts were taken at 0, 6, 12, and 24 h. Approximately 47% of the screened isolates were aerotolerant (viable after a 12-h aerobic incubation period), whereas 24% were hyper-aerotolerant (viable after a 24-h aerobic incubation). A greater prevalence of aerotolerant strains (80%) was found among isolates as compared to isolates (6%). Differences in the oxidative stress response related genes were detected among and isolates when comparative genomics was used to analyze 17 Whole Genome Sequenced (WGS) strains from our laboratory. Genes encoding putative transcriptional regulator proteins and a catalase-like heme binding protein were found in genomes, but were absent in the genomes of . PCR screening showed the presence of a catalase-like protein gene in 75% (68/91) of strains, which was absent in all tested strains. While about 79% (30/38) of the hyper-aerotolerant strains harbored the catalase-like protein gene, the gene was also present in a number of the aerosensitive strains. The Catalase like protein gene was found to be expressed in both aerobic and microaerobic conditions with a 2-fold higher gene expression detected in aerobic conditions for an aerosensitive strain. However, the exact function of the gene remains unclear and awaits further investigation. In conclusion, aerotolerant strains (especially ) are prevalent in various retail meats. Further studies are needed to investigate whether the genes encoding catalase-like heme binding protein and putative transcriptional regulators in strains are involved in stress response.
先前已有关于微需氧菌的耐氧性报道，其耐氧性可提高细菌在压力加工和储存条件下在食品中的存活和传播能力。在本研究中，对167株分离株（76株和91株）进行了耐氧性筛选；这些菌株先前从零售鸡肉、鸡肝、鸡胗、火鸡、猪肉和牛肝样本中分离得到。将细菌培养物在含搅拌的 Mueller Hinton 肉汤中进行需氧培养，并在0、6、12和24小时进行活菌计数。大约47%的筛选分离株具有耐氧性（在需氧培养12小时后仍存活），而24%为超耐氧性（在需氧培养24小时后仍存活）。与分离株（6%）相比，分离株中耐氧菌株的比例更高（80%）。当使用比较基因组学分析我们实验室的17株全基因组测序（WGS）菌株时，在和分离株中检测到氧化应激反应相关基因的差异。在基因组中发现了编码假定转录调节蛋白和过氧化氢酶样血红素结合蛋白的基因，但在基因组中不存在。PCR筛选显示75%（68/91）的菌株中存在过氧化氢酶样蛋白基因，而在所有测试的菌株中均不存在。虽然约79%（30/38）的超耐氧菌株含有过氧化氢酶样蛋白基因，但该基因也存在于一些对氧气敏感的菌株中。发现过氧化氢酶样蛋白基因在需氧和微需氧条件下均有表达，对于一株对氧气敏感的菌株，在需氧条件下检测到的基因表达高出2倍。然而，该基因的确切功能仍不清楚，有待进一步研究。总之，耐氧菌株（尤其是）在各种零售肉类中普遍存在。需要进一步研究来调查菌株中编码过氧化氢酶样血红素结合蛋白和假定转录调节因子的基因是否参与应激反应。
