Search Results

sed -n '/ORGANISM/{n;N;N;N;s/[ \n]//g;s/;/; /g;p;}'

$ cat data
ORGANISM Lates calcarifer
Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi;
...

Try: perl -n0e 'while (/ORGANISM.*?\./sg){$s=$&;$s=~s/\n/ /g;print "$s\n"}' file

It works too:
sed -n '/ORGANISM/{n;N;N;N;s/\n/ /gp}'
readable format:
sed -n '/ORGANISM/ {
n;N;N;N
s/\n/ /gp ...