Specifically methylates the adenine in position 2030 of 23S rRNA. Nascent 23S rRNA seems to be the natural substrate. Appears to be not necessary for ribosome assembly. Required for the utilization of extracellular DNA as the sole source of carbon and energy (PubMed:11591672, PubMed:16707682). adenosine(2030) in 23S rRNA + S-adenosyl-L-methionine = H(+) + N(6)-methyladenosine(2030) in 23S rRNA + S-adenosyl-L-homocysteine Monomer. The inactivation of the this gene results in the complete loss of A2030 modification, but does not cause the accumulation of ribosome assembly intermediates. The phenotype of rlmJ knockout gene is very mild under various growth conditions and at the stationary phase, except for a small growth advantage in anaerobic conditions. Only minor changes in the total E.coli proteome can be observed in a cell devoid of the 23S rRNA nucleotide A2030 methylation (PubMed:22847818). Mutants show a stationary-phase competition defect during coculture with wild-type cells (PubMed:11591672). Cells lacking this gene are unable to grow using DNA as a sole nutrition source, but have no defects in DNA uptake by electroporation or when made chemically competent (PubMed:11591672, PubMed:16707682). Recombinant protein prefers protein-free 23S rRNA to ribonucleoprotein particles containing only part of the 50S subunit proteins and does not methylate the assembled 50S subunit (PubMed:22847818). Recognizes a minimal substrate corresponding to helix 72; this shows that RlmJ requires only a small hairpin for activity and this suggests that RlmJ can methylate A2030 before the 23S RNA is completely transcribed, processed and folded (PubMed:23945937). Cannot modify single-stranded DNA having the same sequence as H72 (PubMed:23945937). Belongs to the RlmJ family.