Aix Marseille Univ., IRD, MEPHI, IHU Méditerranée Infection, Marseille, France.
Université de Montpellier UMR 1058 UMR MIVEGEC, UMR IRD 224-CNRS Inserm, Montpellier, France.
Front Cell Infect Microbiol. 2020 Nov 30;10:519301. doi: 10.3389/fcimb.2020.519301. eCollection 2020.
Traditionally recognized as environmental bacteria, Planctomycetes have just been linked recently to human pathology as opportunistic pathogens, arousing a great interest for clinical microbiologists. However, the lack of appropriate culture media limits our future investigations as no Planctomycetes have ever been isolated from patients' specimens despite several attempts. Several Planctomycetes have no cultivable members and are only recognized by 16S rRNA gene sequence detection and analysis. The cultured representatives are slow-growing fastidious bacteria and mostly difficult to culture on synthetic media. Accordingly, the provision of environmental and nutritional conditions like those existing in the natural habitat where yet uncultured/refractory bacteria can be detected might be an option for their potential isolation. Hence, we systematically reviewed the various natural habitats of Planctomycetes, to review their nutritional requirements, the physicochemical characteristics of their natural ecological niches, current methods of cultivation of the Planctomycetes and gaps, from a perspective of collecting data in order to optimize conditions and the protocols of cultivation of these fastidious bacteria. Planctomycetes are widespread in freshwater, seawater, and terrestrial environments, essentially associated to particles or organisms like macroalgae, marine sponges, and lichens, depending on the species and metabolizable polysaccharides by their sulfatases. Most Planctomycetes grow in nutrient-poor oligotrophic environments with pH ranging from 3.4 to 11, but a few strains can also grow in quite nutrient rich media like M600/M14. Also, a seasonality variation of abundance is observed, and bloom occurs in summer-early autumn, correlating with the strong growth of algae in the marine environments. Most Planctomycetes are mesophilic, but with a few Planctomycetes being thermophilic (50°C to 60°C). Commonly added nutrients are N-acetyl-glucosamine, yeast-extracts, peptone, and some oligo and macro-elements. A biphasic host-associated extract (macroalgae, sponge extract) conjugated with a diluted basal medium should provide favorable results for the success of isolation in pure culture.
传统上被认为是环境细菌的浮霉菌门最近才被发现与人类病理学有关，是机会性病原体，引起了临床微生物学家的极大兴趣。然而，由于缺乏适当的培养基，我们未来的研究受到限制，尽管已经进行了多次尝试，但从未从患者标本中分离出浮霉菌门。一些浮霉菌门没有可培养的成员，只能通过 16S rRNA 基因序列检测和分析来识别。已培养的代表是生长缓慢的苛刻细菌，并且大多难以在合成培养基上培养。因此，提供类似于尚未培养/耐受细菌可检测到的自然栖息地的环境和营养条件可能是潜在分离的一种选择。因此，我们系统地回顾了浮霉菌门的各种自然栖息地，以回顾它们的营养需求、其自然生态位的物理化学特性、浮霉菌门的当前培养方法和差距，从收集数据的角度来看，以便优化这些苛刻细菌的培养条件和方案。浮霉菌门广泛存在于淡水、海水和陆地环境中，主要与颗粒或生物体（如大型藻类、海洋海绵和地衣）相关，具体取决于物种和它们的硫酸盐酶可代谢的多糖。大多数浮霉菌门在营养贫乏的贫营养环境中生长，pH 值范围为 3.4 到 11，但也有少数菌株可以在营养丰富的培养基中生长，如 M600/M14。此外，还观察到丰度的季节性变化，并且在夏季-初秋出现生物量增加，与海洋环境中藻类的强烈生长相关。大多数浮霉菌门是中温的，但也有一些浮霉菌门是嗜热的（50°C 到 60°C）。常用的添加营养物质有 N-乙酰葡萄糖胺、酵母提取物、蛋白胨和一些寡糖和宏量元素。两相宿主相关提取物（大型藻类、海绵提取物）与稀释的基础培养基结合使用，应该为成功分离纯培养物提供有利结果。
