Salmonella enterica Filamentation Induced by Pelargonic Acid Is a Transient Morphotype
Salmonella enterica Filamentation Induced by Pelargonic Acid Is a Transient Morphotype
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DOI：
10.1128/aem.02191-18
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发表时间：
2019-01-01
影响因子：
4.4
通讯作者：
Micallef, Shirley A.
中科院分区：
文献类型：
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作者：
Kumar, Govindaraj Dev;Macarisin, Dumitru;Micallef, Shirley A.
在应激条件下，肠沙门氏菌形成多核细长细丝。细丝形成的诱因和结果还没有很好地描述。研究人员评估了新港、贾维纳和鼠伤寒沙门氏菌血清型在暴露于20mm珀龙酸后形成细丝的能力。以S. Newport为模型，通过可培养群体大小、细胞长度和活力测定来研究丝化的进展和命运。所有血清型在孵育16 h后均显示成丝。经胰大豆肉汤（TSBpel）处理24 h后，胰大豆肉汤（TSBpel）比TSB降低了5 log CFU (P < 0.05)，生长率降低（P < 0.02）。细胞伸长在12 h内开始，16 h达到高峰，20 ~ 24 h出现丝崩解。16 h时，丝与正常大小细胞的比值（F/R）为3.87 +/- 0.59,20和24 h时分别降至0.23 +/- 0.04和0.03 +/- 0.01 （P < 0.05）。添加Mg2+抑制了丝状纤维（F/R = 0.25 +/- 0.11），增加了可培养细胞计数（P < 0.05）。与未添加的培养基相比，持续暴露于天龙酸对TSB和M9的生长有抑制作用（P < 0.05）。而在不添加Mg2+的M9培养基中，添加20 mM的天门冬酸（M9pel），细丝断裂的进展与天门冬酸或Mg2+无关。在营养缺乏的条件下，Mg2+对细胞有积极的影响，在M9中添加5 mM Mg2+ (M9Mg)的细胞活死比高于M9 （P < 0.05）。当添加天竺葵酸时，没有观察到变化。丝状反应在所有血清型中普遍存在，短暂且对Mg2+敏感。无论抗菌剂或Mg2+是否存在，碎裂均有进展，而不是恢复。一些细菌在受到压力时形成细长的多核结构或细丝。丝状食源性细菌病原体可干扰食品保护措施和诊断检测。研究人员研究了新港肠炎沙门氏菌对天门冬酸的反应，天门冬酸是一种天然存在于几种水果和蔬菜中的化合物，也被商业上用作除草剂。沙门氏菌在暴露于天竺葵酸时很容易形成细丝。然而，细丝并不稳定，即使脂肪酸仍然存在，细丝也会分裂成单个细胞，当压力减轻时，细丝会完全恢复。需要对调控成丝的分子机制以及在农业和食品供应链中诱导成丝的条件进行更深入的探索，以制定遏制这种反应的策略。
Under stressful conditions, Salmonella enterica forms multinucleated elongated filaments. The triggers and outcomes of filamentation are not well characterized. S. enterica serotypes Newport, Javiana, and Typhimurium were evaluated for their ability to form filaments upon exposure to 20 mM pelargonic acid. S. Newport was used as a model to investigate the progression and fate of filamentation via culturable population size, cell length, and viability assays. All serotypes displayed filament formation after 16 h of incubation. Pelargonic acid amendment of tryptic soy broth (TSBpel) produced a 5-log CFU reduction compared to TSB after 24 h (P < 0.05), and the growth rate decreased (P < 0.02). Cell elongation started within 12 h, peaked at 16 h, and was followed by filament disintegration at 20 to 24 h. The ratio of filaments to regular-sized cells (F/R) in TSBpel was 3.87 +/- 0.59 at 16 h, decreasing to 0.23 +/- 0.04 and 0.03 +/- 0.01 (P < 0.05) at 20 and 24 h, respectively. Mg2+ supplementation repressed filamentation (F/R = 0.25 +/- 0.11) and enhanced culturable cell counts (P < 0.05). Continued exposure to pelargonic acid inhibited growth in TSB and M9 compared to that in unamended media (P < 0.05). However, in M9 medium without Mg2+ amended with 20 mM pelargonic acid (M9pel), filament fragmentation progressed independently of pelargonic acid or Mg2+. When cells were pretreated with pelargonic acid to induce filamentation and then transferred to fresh medium, a positive effect of Mg2+ was noted under nutrient-deficient conditions, with higher live/dead cell ratios in M9 supplemented with 5 mM Mg2+ (M9Mg) than in M9 (P < 0.05). No change was observed when pelargonic acid was also added. Filamentation was ubiquitous in all serotypes tested, transient, and sensitive to Mg2+. Fragmentation, but not recovery, progressed irrespective of antimicrobial or Mg2+ presence.IMPORTANCE Some bacteria form elongated multinucleated structures, or filaments, when exposed to stress. The filamentous form of foodborne bacterial pathogens can interfere with food protection practices and diagnostic testing. Filamentation in Salmonella enterica Newport was investigated in response to pelargonic acid, a compound naturally found in several fruit and vegetables, and also used commercially as an herbicide. Salmonella readily formed filaments when exposed to pelargonic acid. Filaments were not stable, however, and fragmented to individual cells even when the fatty acid was still present, recovering fully when the stress was alleviated. A deeper exploration of the molecular mechanisms regulating filamentation and the conditions that induce it in agriculture and the food supply chain is needed to devise strategies that curb this response.