不同生物炭对非共生固氮菌定殖分布及固氮效率的影响

Effects of different biochar materials on the colonization pattern and nitrogen fixation efficiency of non-symbiotic nitrogen-fixing bacteria

摘要:

生物炭可作为非共生固氮菌的优良载体，提高微生物的活性和功能特性。然而，非共生固氮菌和生物炭的耦合机制仍不清楚。目的 探究不同生物炭对非共生固氮菌定殖分布及固氮效率的影响。方法 以定殖于玉米秸秆(S)和椴木枯枝(T)生物炭[粒径分级：>2.00 mm (a)、0.25-2.00 mm (b)、<0.25 mm (c)]的非共生固氮菌为研究对象，分析其比表面积和孔隙度的差异，并监测固氮菌数量、pH、可溶性有机碳(dissolved organic carbon, DOC)、可溶性有机氮(dissolved organic nitrogen, DON)、微生物生物量碳(microbial biomass carbon, MBC)、微生物生物量氮(microbial biomass nitrogen, MBN)及固氮酶活性随培养时间延长的动态变化。结果 固氮菌在秸秆炭上的定殖量分布更均匀，且能更好地发挥固氮作用，其中以0.25-2.00 mm粒径的秸秆炭效果更优。相较于木质炭，0.25-2.00 mm粒径秸秆炭负载菌株处理组的MBC平均含量和固氮酶活性分别提高了82.33%-160.55%和231.46%-356.08%。此外，在整个培养期间秸秆炭处理组的DOC和DON含量也显著高于木质炭处理组，为微生物生长提供了可利用的养分。相关性热图分析表明，酸碱性对非共生固氮菌的定殖数量和固氮酶活性具有显著影响；DOC和MBC与固氮酶活性呈强烈显著正相关(P<0.001)，表明高碳生长环境是非共生固氮菌生长和发挥固氮作用的关键因素。结论 玉米秸秆生物炭(0.25-2.00 mm粒径)有利于非共生固氮菌发挥固氮作用，其通过改善微生物的微生态环境提高了微生物的固氮活性和部分功能特性。

Abstract:

Biochar serves as an excellent carrier for non-symbiotic nitrogen (N)-fixing bacteria, enhancing their microbial activity and functions. However, the coupling mechanism between non-symbiotic N-fixing bacteria and biochar remains unclear.Objective To explore the effects of different biochar materials on the colonization pattern and N fixation efficiency of non-symbiotic N-fixing bacteria.Methods Non-symbiotic N-fixing bacteria were inoculated onto biochar samples derived from maize straw and wood chips, the particle sizes of which were >2.00 mm, 0.25-2.00 mm, and <0.25 mm. We compared the porosity and specific surface area of different biochar samples. Throughout the incubation period, the dynamic changes in nitrogenase activity and the number of N-fixing bacteria, pH, dissolved organic carbon (DOC), dissolved organic nitrogen (DON), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) were monitored.Results N-fixing bacteria exhibited more uniform colonization and higher N fixation activity on straw biochar than on woody biochar, especially in the 0.25-2.00 mm group. The straw biochar with the particle size of 0.25-2.00 mm and inoculated with strains showed increases of 82.33%-160.55% and 231.46%-356.08% in the average MBC content and nitrogenase activity, respectively, compared with woody biochar. Moreover, significantly higher content of DOC and DON were maintained in all straw biochar groups, which provided a richer pool of available nutrients for microbial growth. The correlation heatmap indicated that pH significantly affected bacterial colonization and nitrogenase activity. Furthermore, nitrogenase activity showed strong positive correlations with DOC and MBC (P<0.001), which suggested that a carbon-rich environment was a key factor for the growth and N fixation of N-fixing bacteria.Conclusion Straw biochar with the particle size of 0.25-2.00 mm serves as an optimal carrier for non-symbiotic N-fixing bacteria. It provides a favorable microenvironment for the N fixation and some other functions of the bacteria.