酸铝对耐酸苜蓿根瘤菌生长的影响

目的]研究酸性条件和游离铝离子对耐酸苜蓿根瘤菌生长的影响.方法]以普通苜蓿根瘤菌和耐酸根瘤茵为材料,在不同pH液体YMA培养基和加铝酸性液体YMA培养基中进行培养,研究酸铝条件对根瘤菌生长的影响.结果]所有根瘤菌生长都受到酸性条件的限制,但2个耐酸苜蓿根瘤茵受酸性环境影响小,在酸性条件下的生长强度大,最低能耐受pH 3.0的酸度.耐酸苜蓿根瘤菌生长缓滞期比普通根瘤菌短,而且生长缓滞期时间基本不受环境pH的影响,而普通根瘤茵生长缓滞期随pH的降低而延长.在酸性条件下(pH≤5.0),根瘤茵先分泌碱性物质,再分泌酸性物质；在中性条件下,耐酸菌株先分泌酸性物质,再分泌碱性物质,普通菌株持续分泌酸性物质；在碱性条件下(pH 9.0),各菌株持续分泌酸性物质.在pH4.1的酸性条件下,Al3+浓度为0 ～ 0.5 mmol/L时,根瘤菌的生长不受Al3+的影响.结论]酸性条件对耐酸苜蓿根瘤菌生长的影响较普通根瘤菌小,酸性条件下耐酸根瘤菌的生长基本不受游离铝离子影响.

Effects of Acid Environment and Aluminium on the Growth of Rhizobium meliloti

Objective] The research aimed to study the effects of acid condition and free Al3+ on the growth of Rhizobium meliloti.Method] Common Rhizobium meliloti(CR) and acid-tolerant Rhizobium meliloti(ATR) were cultured in different pH liquid YMA medium to study the effects of acid and aluminum on the growth of Rhizobium meliloti.Result] The growth of all Rhizobium meliloti were restricted by acid conditions,but the effects of acid environment on two strains of acid-tolerant R.meliloti was smaller than that of common R.meliloti.Acid-tolerant R.meliloti had greater growth intensity under acid conditions and the lowest pH acidity was 3.0.The lagged phase of ATR was shorter than CR and it was little affected by environmental pH.But the lagged phase of CR was prolonged with the decrease of pH.Under acid conditions(pH≤5.0),all strains of R.meliloti first secreted some alkaline substances and then secreted some acid substances.Under medium conditions,ATR first secreted some acid substances and then secreted some alkaline substances,but CR secreted acid substances from beginning to end.Under alkaline conditions(pH 9.0),all strains of R.meliloti secreted acid substances from beginning to end.Al3+(0-0.5 mmol/L)had no effect on the growth of R.meliloti under acid conditions(pH 4.1).Conclusion] The effects of acid conditions on the growth of ATR was smaller than that of CR and the growth of ATR under acid conditions was little affected by free Al3+.