Effect of soil salinity and nutrient levels on the community structure of the root-associated bacteria of the facultative halophyte, Tamarix ramosissima, in southwestern United States

The Journal of General and Applied Microbiology

Kumud Acharya²  Norikazu Yamanaka¹  Fumiko Iwanaga¹  Takeshi Taniguchi¹  Shogo Imada¹ 

[1] Arid Land Research Center, Tottori University;Division of Hydrologic Sciences, Desert Research Institute

关键词: arbuscular mycorrhizal fungi;    calcium;    phosphorus;    Proteobacteria;    sodium;    Tamarix ramosissima;    terminal restriction fragment length polymorphism analysis;   

DOI  :  10.2323/jgam.61.193

学科分类：微生物学和免疫学

来源: Applied Microbiology, Molecular and Cellulrar Biosciences Research Foundation

【 摘 要 】

Tamarix ramosissima is a tree species that is highly resistant to salt and drought. The Tamarix species survives in a broad range of environmental salt levels, and invades major river systems in southwestern United States. It may affect root-associated bacteria (RB) by increasing soil salts and nutrients. The effects of RB on host plants may vary even under saline conditions, and the relationship may be important for T. ramosissima. However, to the best of our knowledge, there have been no reports relating to T. ramosissima RB and its association with salinity and nutrient levels. In this study, we have examined this association and the effect of arbuscular mycorrhizal colonization of T. ramosissima on RB because a previous study has reported that colonization of arbuscular mycorrhizal fungi affected the rhizobacterial community (Marschner et al., 2001). T. ramosissima roots were collected from five locations with varying soil salinity and nutrient levels. RB community structures were examined by terminal restriction fragment (T-RF) length polymorphism, cloning, and sequencing analyses. The results suggest that RB richness, or the diversity of T. ramosissima, have significant negative relationships with electrical conductivity (EC), sodium concentration (Na), and the colonization of arbuscular mycorrhizal fungi, but have a significant positive relationship with phosphorus in the soil. However, at each T-RF level, positive correlations between the emergence of some T-RFs and EC or Na were observed. These results indicate that high salinity decreased the total number of RB species, but some saline-tolerant RB species multiplied with increasing salinity levels. The ordination scores of nonmetric multidimensional scale analysis of RB community composition show significant relationships with water content, calcium concentration, available phosphorus, and total nitrogen. These results indicate that the RB diversity and community composition of T. ramosissima are affected by soil salinity and nutrient levels. Sequence analysis detected one Bacteroidetes and eight Proteobacteria species. Most 16S rRNA gene sequences had high similarities with the bacteria isolated from saline conditions, indicating that at least a portion of the RB species observed in T. ramosissima was halotolerant.

【 授权许可】

Unknown