Failor K C, Schmale D G, Vinatzer B A, Monteil C L
Department of Plant Pathology, Physiology, and Weed Science, Virginia Tech, Blacksburg, VA, USA.
CNRS/CEA/Aix-Marseille Université, UMR7265 Institut de biosciences et biotechnologies, Laboratoire de Bioénergétique Cellulaire, Saint-Paul-lès-Durance, France.
ISME J. 2017 Dec;11(12):2740-2753. doi: 10.1038/ismej.2017.124. Epub 2017 Jul 28.
A growing body of circumstantial evidence suggests that ice nucleation active (Ice) bacteria contribute to the initiation of precipitation by heterologous freezing of super-cooled water in clouds. However, little is known about the concentration of Ice bacteria in precipitation, their genetic and phenotypic diversity, and their relationship to air mass trajectories and precipitation chemistry. In this study, 23 precipitation events were collected over 15 months in Virginia, USA. Air mass trajectories and water chemistry were determined and 33 134 isolates were screened for ice nucleation activity (INA) at -8 °C. Of 1144 isolates that tested positive during initial screening, 593 had confirmed INA at -8 °C in repeated tests. Concentrations of Ice strains in precipitation were found to range from 0 to 13 219 colony forming units per liter, with a mean of 384±147. Most Ice bacteria were identified as members of known and unknown Ice species in the Pseudomonadaceae, Enterobacteriaceae and Xanthomonadaceae families, which nucleate ice employing the well-characterized membrane-bound INA protein. Two Ice strains, however, were identified as Lysinibacillus, a Gram-positive genus not previously known to include Ice bacteria. INA of the Lysinibacillus strains is due to a nanometer-sized molecule that is heat resistant, lysozyme and proteinase resistant, and secreted. Ice bacteria and the INA mechanisms they employ are thus more diverse than expected. We discuss to what extent the concentration of culturable Ice bacteria in precipitation and the identification of a new heat-resistant biological INA mechanism support a role for Ice bacteria in the initiation of precipitation.
越来越多的间接证据表明，冰核活性（Ice）细菌通过云中过冷水的异源冻结促进降水的开始。然而，关于降水中Ice细菌的浓度、它们的遗传和表型多样性，以及它们与气团轨迹和降水化学的关系，我们所知甚少。在本研究中，在美国弗吉尼亚州的15个月内收集了23次降水事件。确定了气团轨迹和水化学，并在-8°C下对33134个分离株进行了冰核活性（INA）筛选。在初步筛选中检测呈阳性的1144个分离株中，有593个在重复测试中在-8°C下确认具有INA。发现降水中Ice菌株的浓度范围为每升0至13219个菌落形成单位，平均为384±147。大多数Ice细菌被鉴定为假单胞菌科、肠杆菌科和黄单胞菌科中已知和未知的Ice菌种的成员，它们利用特征明确的膜结合INA蛋白使冰成核。然而，有两个Ice菌株被鉴定为赖氨酸芽孢杆菌，这是一个以前未知包含Ice细菌的革兰氏阳性属。赖氨酸芽孢杆菌菌株的INA归因于一种纳米大小的分子，该分子耐热、耐溶菌酶和蛋白酶，并且是分泌型的。因此，Ice细菌及其采用的INA机制比预期的更多样化。我们讨论了降水中可培养Ice细菌的浓度以及新的耐热生物INA机制的鉴定在多大程度上支持Ice细菌在降水开始中的作用。
