Cyanobacteria and heterotrophic bacteria

Cyanobacteria and heterotrophic bacteria have been clubbed together in eubacteria of Kingdom-Monera as per the five kingdom classification even though the two are vastly different from each other. Is this grouping of the two types oftaxa in the same kingdom justified? If so, why?

This is justified as both cyanobacteria and heterotrophic bacteria have prokaryotic nature, possess cell wall with peptidoglycan, 70S ribosomes, without sap vacuoles and membrane covered organelles. Members of Monera have various modes of nutrition as they were the earliest living organisms. The modes of nutrition are anoxygenic photosynthesis, oxygenic photosynthesis, chemosynthesis, heterotrophic nutrition, etc.