auto vacuum question

I have auto vacuum turned on in the postgresql.conf file and I noticed
template1 and postgres databases being vacuumed repeatedly.

Is that necessary? If not, how can I turn it off for just those
databases but not my project's database?



Here are my postgresql.conf autovaccum settings:

autovacuum = on                         # enable autovacuum subprocess?
#autovacuum_naptime = 60                # time between autovacuum runs,
in secs
#autovacuum_vacuum_threshold = 1000     # min # of tuple updates before
                                        # vacuum
#autovacuum_analyze_threshold = 500     # min # of tuple updates before
                                        # analyze
#autovacuum_vacuum_scale_factor = 0.4   # fraction of rel size before
                                        # vacuum
#autovacuum_analyze_scale_factor = 0.2  # fraction of rel size before
                                        # analyze
#autovacuum_vacuum_cost_delay = -1      # default vacuum cost delay for
                                        # autovac, -1 means use
                                        # vacuum_cost_delay
#autovacuum_vacuum_cost_limit = -1      # default vacuum cost limit for
                                        # autovac, -1 means use
                                        # vacuum_cost_limit