Abstract：
Water stress is a major limiting factor for agricultural production under current and projected climate change scenarios. As a sustainable strategy, plant growth-promoting bacterial consortia have been used to reduce plant water stress. However, few studies have examined the effects of stress on multi-trait efficiency and interactivity of bacterial species. In this study, we used several in-vitro experiments, plant assays and greenhouse trials to investigate the effects of stress and bacterial consortia on 1-aminocyclopropane-1-carboxylic acid deaminase (ACCD) activities, indole-3-acetic acid (IAA) production and plant growth-promoting traits (Phosphate-solubilization, starch hydrolysis, siderophores and ammonium production). We further assessed biofilm formation and the chemotactic behaviour in response to ACC. A total of fifteen ACCD rhizobacteria with multiple growth-promoting traits from the dominant plant species from the hyperseasonal Aripo Savannas were screened in this study. Five of the isolates were further analyzed based on their ACCD activities and were tested in single and dual consortium to assess their abilities in promoting growth under simulated drought stress (-0.35 MPa) and chemically induced ACC conditions (0.03 mM). Our findings showed that bacteria which produce high concentrations of IAA affected the isolates\' ability to promote growth under stress, irrespective of microbial combination with ACCD activity above the minimal threshold of 20 nmol α-ketobutyrate mg-1 h-1. Biofilm production with co-culture interaction varied greatly across treatments, however, the general trend showed an increase in biofilm under stress induce conditions. The best performing co-culture, UWIGT-83 and UWIGT-120 (Burkholderia sp.) showed enhanced growth in germination assays and in greenhouse trials with Capsicum chinense (Moruga red hot peppers) under drought stress, when compared to non-inoculated treatments. The findings highlight the importance of testing interactivity of bacterial species with multiple growth promoting traits under stress conditions; and proposed the use of ACC growth media as a novel biofilm screening method for selecting potential stress plant growth-promoting bacteria. Better screening strategies for appropriate plant growth-promoting bacteria may narrow the inconsistency observed between laboratory and field trials.
摘要：
在当前和预计的气候变化情景下，水胁迫是农业生产的主要限制因素。作为一项可持续战略,促进植物生长的细菌聚生体已用于减轻植物水分胁迫。然而,很少有研究研究了应激对细菌多性状效率和相互作用的影响。在这项研究中,我们用了几个体外实验,植物试验和温室试验，以研究胁迫和细菌聚生体对1-氨基环丙烷-1-羧酸脱氨酶（ACCD）活性的影响，吲哚-3-乙酸（IAA）的生产和植物生长促进性状（磷酸盐溶解，淀粉水解，铁载体和铵生产)。我们进一步评估了响应ACC的生物膜形成和趋化行为。在这项研究中，从超季节AripoSavannas的优势植物物种中筛选了15种具有多种促进生长特性的ACCD根际细菌。根据其ACCD活性进一步分析了其中5个分离株，并在单和双联盟中进行了测试，以评估其在模拟干旱胁迫（-0.35MPa）和化学诱导的ACC条件（0.03mM）下促进生长的能力。我们的发现表明，产生高浓度IAA的细菌会影响分离株在胁迫下促进生长的能力，与ACCD活性高于20nmolα-酮丁酸酯mg-1h-1的最小阈值无关。生物膜生产与共培养相互作用在不同的治疗中差异很大，然而,总体趋势显示在应激诱导条件下生物膜增加。表现最好的合作文化，UWIGT-83和UWIGT-120(伯克霍尔德菌）在干旱胁迫下，在发芽试验和辣椒（莫鲁加红辣椒）的温室试验中显示出增强的生长，与非接种处理相比。研究结果强调了在胁迫条件下测试具有多种生长促进性状的细菌物种的相互作用的重要性；并提出了使用ACC生长培养基作为一种新型的生物膜筛选方法来选择潜在的胁迫植物生长促进细菌。更好的筛选适当的植物生长促进细菌的策略可能会缩小实验室和田间试验之间观察到的不一致性。
