An ELISA for the detection of Bacillus subtilis L‐form bacteria confirms their symbiosis in strawberry

Aims: To develop an ELISA for the detection of antigens derived from stable Bacillus subtilis L‐form bacteria and to detect these in plants injected with L‐form bacteria. Methods and Results: A sandwich ELISA was developed and its specificity was investigated using L‐forms and cell‐walled forms of B. subtilis, different Bacillus species and a range of bacteria isolated from glasshouse‐grown strawberry plants. The detection limits of the ELISA were approximately 103 viable cells ml−1 for L‐forms compared with 107 viable cells ml−1 for cell‐walled forms. Results showed that L‐forms survived and moved within strawberry tissues injected with L‐form bacteria. Conclusion: An ELISA that selectively detects B. subtilis L‐form bacteria was developed and shown to confirm the presence of L‐forms in plants. Significance and Impact of the Study: This will be a valuable rapid method to further studies on L‐form plant interactions.