The Blochmann Bodies: Hereditary Intracellular Symbionts of Insects

Abstract

Summary The term ‘Blochmann body’ was originated by Wheeler in 1889 for bacteria‐like particles in the cytoplasm of cockroach eggs. These particles can be traced during embryonic development to definitive somatic cells, the mycetocytes. These and similar particles of other insects have so far not been cultivated in bacteriological media nor injected into host animals to produce either pathological or benign infections. Their structure and composition indicate them to be evolutionary descendants of free‐living micro‐organisms; operationally, they appear to belong to the class of cell particles designated by Lederberg (1952) as plasmids. Genetic studies have shown the Blochmann bodies to be transmitted through the maternal line. Their presence in the egg cytoplasm at some stage in oocyte development is easily demonstrated, but studies by a number of workers have so far yielded a variety of conflicting claims or suggestions as to how the particles get into the germ cells or oocytes. The Blochmann particles of cockroaches, besides existing in the mycetocytes and eggs, occur embedded in a dense tangle of microvilli which are extensions of the plasma membrane of young oocytes. Essentially particle‐free strains of cockroaches can be produced by feeding aureo‐mycin or high levels of urea, or by withholding manganese. The effect is produced only by treating females, and is delayed one generation. In generations following the first (symbiont‐free) generation, the Blochmann symbionts gradually reappear, suggesting that elimination was not absolute. Blochmann bodies in both the mycetocytes and the ovarioles of the cockroach carry out oxidative metabolism, as indicated by their ability to reduce tetrazolium. Glycolysis has not been demonstrated. The generalization that symbionts of the Blochmann type represent an adaptation to compensate for dietary deficiencies is inapplicable, since deficiencies have not been demonstrated for the diets of cockroaches, weevils, or homopterans—the major insect groups in which the symbionts occur. The symbionts of cockroaches and homopterans appear to be involved in the utilization of nitrogenous waste products in synthetic metabolism. In most instances the Blochmann bodies lack the central nucleoid body characteristic of the growing phase of free‐living bacteria, thus resembling the Kappa and Mu particles of Paramecium and the endosymbiont of the protozoan Crithidia oncopelti. Both histochemical tests and electron‐microscope studies indicate a DNA component that is widely dispersed within the particle. Blochmann bodies are without internal cristae. The cockroach symbionts contain muramic acid, a diagnostic feature of the cell wall of bacteria. Response to various nuclear and cytoplasmic reagents is intermediate between those of typical mitochondria and free‐living bacteria. The envelopes of the Blochmann particles are generally thinner than those of free‐living bacteria. The function of plasmids of the Blochmann type may be that they, like the bacteroids of the Rhixobium‐legume symbiosis, ext...

The fate of the endocytobionts ofBlattella germanica(Blattaria: Blattellidae) andperiplaneta Americana(Blattaria: Blattidae) during embryo development

“…The symbionts are transmitted to offspring transovarically. The ways in which this process takes place have been widely studied (see Büchner, 1965;Lanham, 1968), and in particular Sacchi et al (1985Sacchi et al ( , 1988 have described the various stages of the bacterial cycle which ends with the symbiotic bacteria's passing into the egg.…”

Nitrogen recycling and nutritional provisioning byBlattabacterium, the cockroach endosymbiont

“…Similarly, Reticulitermes flavipes hindgut bacteria ferment uric acid transported from the fat bodies, via the Malpighian tubules to the hindgut, into ammonia, CO 2 , and acetate (6)(7)(8). Cockroaches, close relatives of termites, harbor intracellular, maternally transmitted bacteria, called Blattabacterium sp., within their fat bodies, near the uric acid deposits (9), and they have been hypothesized to participate in nitrogen recycling from stored uric acid (10,11). Periplaneta americana fat bodies are comprised of two distinct cell types: adipocytes, containing fat globules and uric acid crystals, and mycetocytes, which are filled densely with Blattabacterium (9,(11)(12)(13).…”

“…Cockroaches, close relatives of termites, harbor intracellular, maternally transmitted bacteria, called Blattabacterium sp., within their fat bodies, near the uric acid deposits (9), and they have been hypothesized to participate in nitrogen recycling from stored uric acid (10,11). Periplaneta americana fat bodies are comprised of two distinct cell types: adipocytes, containing fat globules and uric acid crystals, and mycetocytes, which are filled densely with Blattabacterium (9,(11)(12)(13). After antibiotic treatment to remove Blattabacterium, mycetocytes appear to be highly degraded, uric acid accumulates significantly (13)(14)(15), and production of tyrosine, phenylalanine, isoleucine, valine, arginine, and threonine is reduced (16).…”

Tissue Localization of the Endosymbiotic Bacterium “ Candidatus Blochmannia floridanus” in Adults and Larvae of the Carpenter Ant Camponotus floridanus

“…The endosymbiotic bacteria of Camponotus species are gram-negative rods of variable length which apparently float freely in the cytoplasm of the host cells (18). The cytoplasmic location of the bacteria in Camponotus bacteriocytes distinguishes this symbiosis from other bacteriocyte symbioses in which the bacteria exist within membrane-surrounded compartments, the so-called symbiosomes (6,14).…”