Attachment of diaminopimelic acid to bdelloplast peptidoglycan during intraperiplasmic growth of Bdellovibrio bacteriovorus 109J

Abstract

An early event in the predatory lifestyle of Bdellovibrio bacteriovorus 109J is the attachment of diaminopimelic acid (DAP) to the peptidoglycan of its prey. Attachment occurs over the first 60 min of the growth cycle and is mediated by an extracellular activity(s) produced by the bdellovibrio. Some 40,000 DAP residues are incorporated into the Escherichia coli bdelloplast wall, amounting to ca. 2 to 3% of the total initial DAP content of its prey cells. Incorporation of DAP occurs when E. coli, Pseudomonas putida, or Spirillum serpens are the prey organisms. The structurally similar compounds lysine, ornithine, citrulline, and 2,4-diaminobutyric acid are not attached. The attachment process is not affected by heat-killing the prey nor by the addition of inhibitors of either energy generation (cyanide, azide, or arsenate), protein or RNA synthesis (chloramphenicol and rifamycin), or de novo synthesis of cell wall (penicillin or vancomycin). Approximately one-third of the incorporated DAP is exchangeable with exogenously added unlabeled DAP, whereas the remaining incorporated DPA is solubilized only during the lysis of the bdelloplast wall. Examination of DAP incorporation at low prey cell densities suggests that bdellovibrios closely couple the incorporation to an independent, enzymatic solubilization of DAP by a peptidase. The data indicate that DAP incorporation is a novel process, representing the second example of the ability of the bdellovibrio to biosynthetically modify the wall of its prey. 1010 cells per ml (8.9 x 107 cpm/ml) in HM buffer. Chemicals. Radiolabeled [G-3H]DAP and [U-_4C]D-alanine were obtained from Amersham Corp., Arlington Heights, Ill., and [1-14C]glucosamine was obtained from New England Nuclear Corp., Boston, Mass. Penicillin G, vancomycin, bacitracin, cycloserine, and chloramphenicol were obtained from Sigma Chemical Co., St. Louis, Mo. Rifamycin (stock solution made daily as 5 mg/ml in 70% ethanol) was obtained from Calbiochem-Behring Corp., La Jolla, Calif.

Insight into the Possible Use of the Predator Bdellovibrio bacteriovorus as a Probiotic

“…The signal for the start of the process is still unknown but seems to be related to the penetration of the prey, bdelloplast formation, and the prey's nutrient consumption [67]. The second signal, released by the prey, is hypothesized to be soluble and to promote DNA synthesis, which is essential for the sustainment of the actively growing phase [68,69]. Rotem and collaborators revealed the existence of an intermediate phase between the first and the second signal that seems to be decisive for the start of the GP phase by the predator.…”

Comparative biology of intracellular parasitism.

“…The entry-associated breakdown of peptidoglycan by glycanase (401) is terminated by the action of another bdellovibrio enzyme that hydrolyzes N-acetyl groups from the peptidoglycan (402), thus making it an unfit substrate for glycanase. Bdellovibrio enzymes also bring about the addition of diaminopimelic acid (356) and longchain fatty acids (403) to the bdelloplast wall. Other bdellovibrios that subsequently encounter the bdelloplast cannot make holes in the deacetylated peptidoglycan, and so the first bdellovibrio on the scene does not have to share the resources of the host cell with latecomers.…”

“…Infectious, flagellated bdellovibrios do not make DNA (338,356), and although structural modification of host membranes begins as early as 20 min after entry into the bacterial host, DNA synthesis and filamentous growth do not start for another 40 min (259). These observations have been interpreted to mean that bdellovibrios must be in the intraperiplasmic space for about 1 h before they become responsive to a signal for starting DNA synthesis that is received only in that habitat (346, 355).…”

“…-When filamentous, growing bdellovibrios are prematurely released from host bacteria, they complete one round of DNA replication and then fragment into infectious forms in the absence of external sources of carbon for energy or of any special stimulating factor (356). It appears that, for the prematurely released bdellovibrios, the signal for cessation of multiplication and onset of differentiation is removal from their normal habitat and that, for the bdellovibrios left undisturbed in the intraperiplasmic space, the corresponding signal is exhaustion of a regulatory component (356). Exhaustion of a metabolite or inactivation of a regulator is also the best guess as to what controls differentiation of schizonts into merozoites and reticulate bodies into elementary bodies.…”

Comprehensive analysis of transport proteins encoded within the genome of Bdellovibrio bacteriovorus

“…Since B. bacteriovorus can synthesize only 11 amino acids, protein synthesis depends on the uptake of host degradation products [11]. (5) Bdelloplast formation: The rod-shaped host cell rounds up into the spherical bdelloplast [2,15], and cell growth continues. (6) Septation: After formation of a single long snake-like cell, B. bacteriovorus synchronously undergoes septation, generating multiple progeny cells.…”