Bacterial cell shapes may be altered by the cell cycle, nutrient availability, environmental stress, and interactions with other organisms. The bean bug Riptortus pedestris possesses a symbiotic bacterium, Burkholderia insecticola, in its midgut crypts. This symbiont is a typical rod-shaped bacterium under in vitro culture conditions, but changes to a spherical shape inside the gut symbiotic organ of the host insect, suggesting the induction of morphological alterations in B. insecticola by host factors. The present study revealed that a deletion mutant of a peptidoglycan amidase gene (amiC), showing a filamentous chain form in vitro, adapted a swollen L-form-like cell shape in midgut crypts. Spatiotemporal observations of the ΔamiC mutant in midgut crypts revealed the induction of swollen cells, particularly prior to the molting of insects. To elucidate the mechanisms underlying in vivo-specific morphological alterations, the symbiont was cultured under 13 different conditions and its cell shape was examined. Swollen cells, similar to symbiont cells in midgut crypts, were induced when the mutant was treated with fosfomycin, an inhibitor of peptidoglycan precursor biosynthesis. Collectively, these results strongly suggest that the Burkholderia symbiont in midgut crypts is under the control of the host insect via a cell wall-attacking agent.

中文翻译：

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昆虫伯克霍尔德菌的肽聚糖酰胺酶突变体适应豆pedRiptortus pedestris的肠道共生器官中的L形形状。

细菌细胞的形状可能会因细胞周期，养分利用率，环境压力以及与其他生物的相互作用而改变。豆虫Riptortus pedestris在其中肠隐窝中拥有一种共生细菌，即伯克霍尔德氏菌。这种共生菌在体外培养条件下是典型的杆状细菌，但是在寄主昆虫的肠道共生器官内部变成球形，这表明寄主细菌可诱导昆虫昆虫双歧杆菌发生形态学改变。本研究表明，肽聚糖酰胺酶基因（amiC）的缺失突变体在体外呈丝状链状，在中肠隐窝中适应了肿胀的L型样细胞形状。在中肠隐窝中的ΔamiC突变体的时空观察表明，诱导了肿胀的细胞，特别是在昆虫蜕皮之前。为了阐明体内特异性形态改变的潜在机制，共生体在13种不同条件下培养，并检查了其细胞形状。当用肽聚糖前体生物合成抑制剂磷霉素处理该突变体时，会诱导出类似于中肠隐窝共生细胞的肿胀细胞。总体而言，这些结果强烈表明中肠隐窝中的伯克霍尔德菌共生体通过细胞壁攻击剂受到宿主昆虫的控制。