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Identification of a hormogonium polysaccharide-specific gene set conserved in filamentous cyanobacteria.
Molecular Microbiology ( IF 2.6 ) Pub Date : 2020-07-02 , DOI: 10.1111/mmi.14566
Esthefani G Zuniga 1 , Kelvin K A Boateng 1 , Nhi U Bui 1 , Shadi Kurnfuli 1 , Sawsan M Muthana 1 , Douglas D Risser 1
Affiliation  

Cyanobacteria comprise a phylum defined by the capacity for oxygenic photosynthesis. Members of this phylum are frequently motile as well. Strains that display gliding or twitching motility across semisolid surfaces are powered by a conserved type IV pilus system (T4P). Among the filamentous, heterocyst‐forming cyanobacteria, motility is usually confined to specialized filaments known as hormogonia, and requires the deposition of an associated hormogonium polysaccharide (HPS). The genes involved in assembly and export of HPS are largely undefined, and it has been hypothesized that HPS exits the outer membrane via an atypical T4P‐driven mechanism. Here, several novel hps loci, primarily encoding glycosyl transferases, are identified. Mutational analysis demonstrates that the majority of these genes are essential for both motility and production of HPS. Notably, most mutant strains accumulate wild‐type cellular levels of the major pilin PilA, but not extracellular PilA, indicating dysregulation of the T4P motors, and, therefore, a regulatory interaction between HPS assembly and T4P activity. A co‐occurrence analysis of Hps orthologs among cyanobacteria identified an extended set of putative Hps proteins comprising most components of a Wzx/Wzy‐type polysaccharide synthesis and export system. This implies that HPS may be secreted through a more canonical pathway, rather than a T4P‐mediated mechanism.

中文翻译:

鉴定丝状蓝细菌中保守的属多糖特异性基因集。

蓝细菌包括由氧光合作用的能力定义的门。该门的成员也经常运动。在保守的IV型菌毛系统(T4P)的驱动下,在半固体表面上显示出滑动或抽搐运动的菌株。在丝状,形成异囊的蓝细菌中,运动性通常仅限于称为“激素”的特殊丝,并且需要沉积相关的多糖(HPS)。HPS组装和输出中涉及的基因尚不清楚,并且据推测,HPS通过非典型的T4P驱动机制从外膜出来。在这里,几个新颖的马力确定了主要编码糖基转移酶的基因座。突变分析表明,这些基因中的大多数对于HPS的活力和产生都是必不可少的。值得注意的是,大多数突变菌株在主要菌毛蛋白PilA上积累了野生型细胞水平,但在细胞外PilA上却没有积累,表明T4P马达失调,因此,HPS装配与T4P活性之间存在调节相互作用。蓝细菌之间的Hps直系同源物的共现分析确定了一组扩展的推定Hps蛋白,其中包含Wzx / Wzy型多糖合成和输出系统的大多数成分。这意味着HPS可能通过更规范的途径分泌,而不是通过T4P介导的机制分泌。
更新日期:2020-07-02
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