This protocol was used to express a gene encoding a silaffin precursor TpSil3p-APEX2 fusion protein in T. pseudonana strain CCMP1335 via conjugation largely following Karas et al. (2015). In addition to the protocol I am listing some of my observations working with this diatom species. Please check the 'Before start' and 'Guidelines' sections.\u00a01. B. J. Karas et al., Designer diatom episomes delivered by bacterial conjugation. Nat. Commun. 6, 6925 (2015).