莱氏野村菌cq菌株感染家蚕的特性及菌株产生的晶体

Characterization of Silkworm Infected by Nomuraea rileyi Strain cq and Crystals Produced by the Infection

莱氏野村菌(Nomuraea rileyi)cq菌株为昆虫致病性真菌,能感染家蚕发生绿僵病。显微镜下观察菌株体外培养产生的分生孢子呈卵圆形或椭圆形,大小为3.2～4.6μm×2.5～3.2μm,分生孢子梗单生,具有3～4个轮状分支,每个分支着生2～3个瓶梗,瓶梗基部膨大,在瓶梗顶端尖处着生分生孢子。在感染莱氏野村菌的家蚕幼虫血液中可观察到菌株产生的大量豆荚状、酵母状芽生孢子,病蚕血液呈浑浊的乳白色,体表出现褐色病斑,反应迟缓,尸体逐渐僵化,被鲜绿色的孢子粉覆盖。另发现该菌株在感染家蚕幼虫的体表和血液中能产生菱形晶体,同时菌株在体外培养基上培养时也观察到大量的正八面体菱形晶体,且改变培养温度和pH值,晶体产生的时间延长,形状和大小也会发生变化,出现长方形、正方形六面体形状及不规则形状晶体。推测莱氏野村菌cq菌株产生的晶体可能是有利于菌株感染家蚕的一种次生代谢产物。

Nomuraea rileyi strain cq is an entomopathogenic fungus capable of infecting silkworm to cause green muscardine disease.Under microscope,the conidia of cultured Nomuraea rileyi measured 3.2~4.6 μm × 2.5~3.2 μm which was ellipsoidal or ovoid in shape.The mono-phialidic conidiophore contained 3~4 verticillate branches with 2~3 phialides developed in each branch.The base of phialide was inflated and the conidia were developed on the top of phialide.In the hemolymph of silkworm larvae infected by Nomuraea rileyi,a large quantity of pod-shaped and yeast-like blastospores were observed.The hemolymph of infected larvae appeared milky white with turbidity.The infected larvae had dark brown disease spots on their body surface and were slow in response.The dead bodies became stiff gradually and were covered by green conidial powder.Diamond-shaped crystals were observed both on the body surface and in the hemolymph of silkworm larvae infected by Nomuraea rileyi.Meanwhile,it was observed that the cultured fungi also produced a large number of octahedral diamond-shaped crystals.Nevertheless,if temperature for the culture and pH value of the medium were changed,the time needed to form crystals,and the size and shape of the formed crystals would be changed.Other shapes of the crystals included rectangle,square hexahedron and irregular forms.It is suggested that the crystals produced by Nomuraea rileyi strain cq is a secondary metabolite favorable for the fungus to infect silkworm larvae.