hwo to use different font size and emphasis in src snippets?

[Luca Ferrari <fluca1978@gmail.com>]

Hi all,
I'd like to make my presentations a little more appealing. I've got
code snippets like the following:

#+begin_src shell
% pgbench -i -s 30 -F 100 --foreign-keys -h 127.0.0.1 -U luca pgbench
generating data...
100000 of 3000000 tuples (3%) done (elapsed 0.09 s, remaining 2.64 s)
200000 of 3000000 tuples (6%) done (elapsed 0.14 s, remaining 1.94 s)
300000 of 3000000 tuples (10%) done (elapsed 0.18 s, remaining 1.66 s)
...
vacuuming...
creating primary keys...
creating foreign keys...
done.
#+end_src


I would like to:
1) put an emphasis on the command line (first line), let's say to put
it in bold;
2) use a smaller font for the command output without reducing the font
size of the command line.

Of course, the export is in beamer.
Is it possible? Any suggestions?

Thanks,
Luca