endophyte
Schulz, B., Boyle, C. (2006). What are Endophytes?. In: Schulz, B.J.E., Boyle, C.J.C., Sieber, T.N. (eds) Microbial Root Endophytes. Soil Biology, vol 9. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-33526-9_1
“…bacteria and fungi that can be detected at a particular moment within the tissues of apparently healthy plant hosts”