Does yeast grow on LB agar plates?
Not well, they need  dextrose. Use YBT:

20 g Casein Peptone Tpe-M
10 g Yeast Extract
20 g Dextrose
17 g Agar

q.s. to 975 mls in di-water.

pH to 6.2 w 5M NaOH

q.s. to 1L with di-water.

Autoclave for 45 min at 121C

Aseptically dispense in Petri dishes.

Store at 4C for up to 12 weeks.

If you want to grow Co-culture do so in LB supplemented with 20g/L Dex.