Respiration of Bdellovibrio bacteriovorus Strain 109J and Its Energy Substrates for Intraperiplasmic Growth

Abstract

Measurements of oxidation rates, respiratory quotients (RQ), and release of 14 CO 2 from uniformly labeled substrates showed that glutamate, α-ketoglutarate, and synthetic and natural amino acid mixtures are oxidized by suspensions of Bdellovibrio bacteriovorus strain 109J. The oxidation of these substrates largely suppress the endogenous respiration of the Bdellovibrio cells and may or may not cause a small increase, 20 to 50%, in their rate of oxygen consumption. The failure of respired substrates to increase markedly the respiration rate of the Bdellovibrio cells over the endogenous value is discussed. Carbon from these substrates is incorporated into the Bdellovibrio cells during oxidation. Acetate is also oxidized, but its oxidation inhibits endogenous respiration by only about 40% and no acetate is assimilated. The RQ of the Bdellovibrio cells changes from a value characteristic of endogenous respiration to that characteristic of the oxidation of glutamate or of a balanced amino mixture very shortly after the attack of the Bdellovibrio cells on their prey, and the latter RQ is maintained during intraperiplasmic growth. Glutamate, or a mixture of amino acids in the external environment, contributes to the carbon dioxide produced by the Bdellovibrio cells growing intraperiplasmically. It is concluded from these data that amino acids, derived from the breakdown of the protein of the prey, serve as a major energy source during intraperiplasmic growth of B. bacteriovorus 108J. Insofar as they were tested, B. bacteriovorus strains 109D and A. 3. 12 were similar in respiration to strain 109J.

Regulated breakdown of Escherichia coli deoxyribonucleic acid during intraperiplasmic growth of Bdellovibrio bacteriovorus 109J

“…The exoenzymes responsible for the degradation of substrate cell macromolecules must be released by the bdellovibrio into what was the periplasmic space or the protoplast of the attacked cell or into both and must be retained there. Included among these enzymes would be proteases, known to be produced by the bdellovibrios (11,12,19), which generate the amino acids used for biosynthesis and energy production (17). These could act not only on substrate cell proteins, including the substrate cell's DNases, whose inactivation was discussed above, but also on the other exoenzymes introduced by the bdellovibrio into the bdelloplast chamber.…”

Chemotaxis toward amino acids by Bdellovibrio bacteriovorus

“…bacteriovorus is extremely limited. Hespell et al (6) have shown that glutamate is readily oxidized by the obligately predacious B. bacteriovorus strain 109J, and alanine and tryptophan are only slowly oxidized. None of these amino acids is attractive to B. bacteriovorus strain UKi2.…”

“…To understand the survival value of chemotaxis for B. bacteriovorus, it would be useful to know what types of compounds are attractive to bdellovibrios. It has previously been shown that these cells can oxidize and incorporate amino acids but do not incorporate carbohydrates (6), and that starvation of bdellovibrios in the absence ofprey is relieved by amino acids (7). Furthermore, some amino acids serve as attractants as well as sources of carbon and energy for potential prey cells such as Escherichia coli (8) and Salmonella typhimurium (3).…”

Response of Neisseria gonorrhoeae to Bdellovibrio species

“…Bdellovibrio species are ubiquitous aerobic gram-negative bacteria, extremely small, that attack and infect other bacteria by growing in the space between their cell wall and cell membrane (13). The relationship is more accurately that of predator-prey than parasite-host (2). After an often violent, and perhaps chemotactically mediated, collision between rapidly moving bdellovibrios and their targets (15), attachment occurs via several pilus-like filaments (13,15).…”

“…When gonococci were mixed with more natural target bacilli for individual bdellovibrios, there was rapid attachment and penetration of the gramnegative rods by the bdellovibrios, whereas gonococci (and S. aureus 502A and L. monocytogenes) were ignored. Failure of bdellovibriogonococcal interaction occurred regardless of gonococcal colony morphology (Ti, T2, or T3), piliation (Ti), penicillin susceptibility, or mo- 2 1/0…”