"Candidatus Karelsulcia muelleri" is an aerobic, gram-negative, bacillus bacterium that is a part of the phylum Bacteroidota.
K. muelleri" is an obligate and mutualistic symbiotic microbe commonly found occupying specialized cell compartments of sap-feeding insects called bacteriocytes.
[5][6][7][8] Other studies have documented the nature of its residency in other insects like the maize leafhopper (Cicadulina) or the spittlebug (Cercopoidea).
[2] The genus "Candidatus Sulcia" is named after Vytváření Karel Šulc, a Moravian embryologist who was one of the first scientists to recognize that the insect bacteriome is an organ where bacteria reside.
Karelsulcia" in 2017 to avoid breach of the nomenclatural code, as Sulcia is already a genus of spiders.
[3] The species, muelleri, has been named in the honor of H. J. Müller, (not to be confused with Hermann Joseph Muller) who speculated in 1960 that there was a parallel evolutionary history between endosymbionts and a select clade of insect hosts known as Auchenorrhyncha.
K. muelleri" lacks most of the genes responsible for cell division and membrane synthesis, it is sometimes observed to extend to unusual lengths of up to 100 μm during part of its life cycle.
K. muelleri" and its host leave cofactor and vitamin production to another member of the symbiotic relationship.
The tree was constructed by comparing the peptide sequences of ten different types of proteins.
K. muelleri" branch is that there has been a high frequency of base-pair substitution which has led to noticeable genetic differences between "Ca.
[8] Croceibacter Gramella Cellulophaga Robiginitalea Flavobacterium Polaribacter "Candidatus Karelsulcia" Bacteroides Prevotella Algoriphagus Microscilla Cytophaga Salinibacter Phylogeny using 120 bacterial markers from known genomes (see GTDB) place the bacterium under family Blattabacteriaceae.
Using 11 full genomes of acceptable quality, the database is able to define two species-level groups.
K. muelleri" genome is what scientists refer to as a reduced genome; it is categorized by the apparent evolutionary loss of many ostensibly essential genes related to processes like DNA repair, translation or cell membrane biosynthesis.
[8] The conditions required for genome reduction can be multifaceted, however they often involve some form of stability.
K. muelleri" and "Candidatus Zinderia insecticola" are both found to live in the bacteriome of select species of the spittlebug.
All symbionts appear to possess a reduced genome, have a high GC-content and bear a more frequent base-pair substitution rate compared to their free-living ancestors.
[8] Because of symbiosis, hosts may be able to utilize metabolic pathways they might not be able to use if their endosymbionts were absent; one relevant example is the ability for sap-feeding insects to survive off of relatively nutrient-poor food sources, e.g. xylem and phloem.
K. muelleri" is always found inside the bacteriocyte of a host along with at least one other endosymbiont; The GSWW strain of "Ca.
[8] Genomic analysis has revealed the respective metabolic roles for each other members of this symbiotic triangle.
[8] The glassy-winged sharpshooter, which feeds on the xylem of plants, supplies simple amino acids and carbon sources for the two endosymbionts.
K. muelleri" uses the basic materials to synthesize complex amino acids like homoserine or L-threonine.
[8] One unanswered question about this symbiotic relationship asks how the endosymbionts receive a sufficient amount of nitrogen.
[8] Listed below is a model of the symbiotic metabolic exchange based on the metabolites that are used by "Ca.
K. muelleri", strain GWSS's reduced genome suggests that a proportionate amount of the genes preserved over its evolution are dedicated to amino acid biosynthesis.
K. muelleri" is usually capable of synthesizing 8 of its essential amino acids: leucine, valine, threonine, isoleucine, lysine, arginine, phenylalanine, and tryptophan.
[8] Sulcia muelleri is responsible for making two complex amino acids for its host: homoserine and 2-ketovaline.
K. muelleri" lacks a full set of Aminoacyl tRNA synthetases; surprisingly, however, it possesses all of the genes necessary to code for all 20 amino acids.