Artist: Bob Marley
Song: Walk The Proud Land
Album: Talkin' Blues

The main bassline for the tune goes like:

G----------------------------------
D----------------------------------
A-7-57-57----------7-57-57---------
E---------5(5)5(5)---------5(5)5(5)

The tune drops into the key of B every now and then for a couple rounds:

G----------------------------------
D----------------------------------
A----------------------------------
E-7-57-57-0(0)0(0)-7-57-57-0(0)0(0)

..but it kinda sounds like he's using a 5-string:

G----------------------------------
D----------------------------------
A----------------------------------
E-7-57-57----------7-57-57---------
B---------5-3-5(5)---------5-3-5(5)