Protist both microbial eukaryotes and macroscopic organisms that do not fit into the other traditional kingdoms. In cladistic systems (classifications based on common ancestry), there are no equivalents to the taxa Protista or Protoctista, both terms referring to a paraphyletic group that spans the entire eukaryotic tree of life. In cladistic classification, the contents of Protista are distributed among various "supergroups" (SAR, such as protozoa and some algae, Archaeplastida, such as land plants and some algae, Excavata, which are a group of unicellular organisms, and Opisthokonta, such as animals and fungi, etc.). "Protista", <nowiki>"Protoctista"</nowiki> and "Protozoa" are considered obsolete. However, the
Mycorrhiza helper bacteria fact, the plant could grow with the presence of multiple bacteria. It has been hypothesized that rhizosphere helper bacteria, in the soil, have developed traits to aid them in competition for inoculating fungi in their environment. Thus, it is plausible that MHBs select for certain fungi and developed some specificity towards a fungus that favours the bacteria. MHB help mycorrhiza establish symbiotic associations in stressful environments such as those high in toxic metals. In harsh environments, the bacteria assist in acquiring more nutrients such as nitrogen and phosphorus. MHB helps to prevent the uptake of toxic metals including lead, zinc,