Agar, a commercial product extensively used to grow microbes and in...

Agar is a commercial product obtained from red algae (Rhodophyceae), specifically from the genera $Gelidium$ and $Gracilaria$.

It is extensively used as a solidifying agent in culture media to grow microbes and in the food industry for the preparation of ice-creams and jellies.

$Laminaria$ and $Sargassum$ are brown algae that produce algin.

$Chlorella$ and $Spirulina$ are unicellular organisms rich in proteins and are used as food supplements.

Answer: $Gelidium$ and $Gracilaria$