Rajendran Geetha, Sing Falguni, Desai Anjana J, Archana G
Department of Microbiology and Biotechnology Centre, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara 390 002, Gujarat, India.
Bioresour Technol. 2008 Jul;99(11):4544-50. doi: 10.1016/j.biortech.2007.06.057. Epub 2007 Sep 10.
Endophytic bacteria which are known to reside in plant tissues have often been shown to promote plant growth. Present study deals with the isolation of putative endophytes from the surface sterilized root nodules of pigeon pea (Cajanus cajan) designated as non-rhizobial (NR) isolates. Three of these non-rhizobial isolates called NR2, NR4 and NR6 showed plant growth promotion with respect to increase in plant fresh weight, chlorophyll content, nodule number and nodule fresh weight when co-inoculated with the rhizobial bioinoculant strain IC3123. The three isolates were neither able to nodulate C. cajan nor did they show significant plant growth promotion when inoculated alone without Rhizobium spp. IC3123. All the three isolates were gram positive rods with NR2 and NR4 showing endospore formation and formed one single cluster in Amplified Ribosomal DNA Restriction Analysis (ARDRA). Partial sequences of 16S rRNA genes of NR4 and NR6 showed 97% similarity to Bacillus megaterium. The Bacillus strains NR4 and NR6 were able to produce siderophores which the rhizobial bioinoculant IC3123 was able to cross-utilize. Under iron starved conditions IC3123 showed enhanced growth in the presence of the Bacillus isolates indicating that siderophore mediated interactions may be underlying mechanism of beneficial effect of the NR isolates on nodulation by IC3123.
已知存在于植物组织中的内生细菌常常被证明能促进植物生长。本研究涉及从经过表面消毒的木豆（Cajanus cajan）根瘤中分离假定的内生菌，这些内生菌被指定为非根瘤菌（NR）分离株。其中三个非根瘤菌分离株NR2、NR4和NR6，在与根瘤菌生物接种菌株IC3123共同接种时，在植物鲜重、叶绿素含量、根瘤数量和根瘤鲜重增加方面表现出促进植物生长的作用。这三个分离株既不能使木豆结瘤，在不与根瘤菌属IC3123共同接种而单独接种时，也未表现出显著的植物生长促进作用。所有这三个分离株均为革兰氏阳性杆菌，NR2和NR4表现出芽孢形成，并且在扩增核糖体DNA限制性分析（ARDRA）中形成一个单一聚类。NR4和NR6的16S rRNA基因部分序列与巨大芽孢杆菌显示出97%的相似性。芽孢杆菌菌株NR4和NR6能够产生铁载体，根瘤菌生物接种剂IC3123能够交叉利用这些铁载体。在缺铁条件下，IC3123在芽孢杆菌分离株存在时生长增强，这表明铁载体介导的相互作用可能是NR分离株对IC3123结瘤产生有益作用的潜在机制。
