An ATP transport system in the intracellular bacterium, Bdellovibrio bacteriovorus 109J

Abstract

The intracellularly growing bacterium Bdellovibrio bacteriovorus 109J transports intact ATP by a specific, energy-requiring process. ATP transport does not involve either an ADP-ATP or ah AMP-ATP exchange mechanism but, instead, has characteristics of an active transport permease. Kinetically distinct systems for ATP transport are expressed by the two developmental stages of the bdellovibrio life cycle. In cell suspensions to which y-abeled ATP was added there was a roughly linear uptake Of 32p for 1 or 2 min that was not influenced by the addition of 0.1 mM potassium phosphate to the suspension (Fig. la). This indicated that the 32p label was not being transported after hydrolysis to Pi. In addition, the observed rate of [y32P]ATP accumulation (148 pmol/min per mg of protein) was almost identical to the rate of accumulation of ATP that was labeled with 3H in the adenine ring (164 pmol/min per mg of protein) (Fig. lb). These two results are consistent with the conclusion that bdellovibrio cells transport ATP as an intact molecule. The accumulation was a temperature-dependent process and was sensitive to respiratory inhibitors such as cyanide (Fig. la), azide, and the proton gradient uncoupler carbonyl cyanide m-chlorophenyl hydrazone (data not shown).To demonstrate that a compoutd is accumulated by active transport, it must be shown both that a radioactive label is concentrated intracellularly and that the label is in a chemically unaltered form. Over 94% of the total radioactivity taken up by bdellovibrios exposed to.[3H]ATP for 1 min was present in the trichloroacetic acid-soluble fraction of the cell contents. Chromatography of this fraction by reverse-phase high-performance liquid chromatography (19) revealed that essentially all of the label conmigrated with authentic ATP (Fig. 2). By using an internal volume of 1 4ul/1010 cells (19), it is possible to calculate that the internal concentration of labeled ATP after 1 min of accumulation was 5.5 times the concentration of ATP in the suspending medium. Thus bdellovibrios have the capacity to internally concentrate intact ATP against a gradient.During the course of their unique developmental life cycle bdellovibrios exist in two differentiated forms: an intracellular growth-phase cell and an extracellular attack-phase cell

Verification of the protein in the outer membrane of Bdellovibrio bacteriovorus as the OmpF protein of its Escherichia coli prey

“…This efficiency is accomplished in part by the ability of the organism to recycle prey components without excessive degradation (9,11,14,15). Consistent with this theme are the observations by Guerrini et al.…”

Evidence for adenylate nucleotide transport (ATP-ADP translocation) in vesicles of Frankia sp. strain EAN1pec

“…The rate of ATP uptake (220 pmol of ATP/min per mg of protein) by isolated vesicles of Frankia spp. is similar to the rates reported for cells of Rickettsia prowazekii, Clamydia psittaci, and Bdellovibrio bacteriovorus (9,25,37).…”

“…(9,36,37) and in the energy-generating mitochondria and chloroplasts of eucaryotic cells (10,34,38). Bdellovibrio spp., the intraperiplasmic parasites of gram-negative bacteria, accumulate ATP by a mechanism that is not an ATP translocase (25). The rate of ATP uptake (220 pmol of ATP/min per mg of protein) by isolated vesicles of Frankia spp.…”

Protein uptake into E. coll during Bdellovibrio infection

“…phate uptake system, correlates with the unusual, exclusively parasitic lifestyle of B. bacteriovorus [30,31].…”