Bdellovibrio, δ-proteobacteria, including B. bacteriovorus (Bba) and B. exovorus (Bex), are obligate predators of other Gram-negative bacteria. While Bba grows in the periplasm of the prey cell, Bex grows externally. We have analyzed and compared the transport proteins of these 2 organisms based on the current contents of the Transporter Classification Database (TCDB; www.tcdb.org). Bba has 103 transporters more than Bex, 50% more secondary carriers, and 3 times as many MFS carriers. Bba has far more metabolite transporters than Bex as expected from its larger genome, but there are 2 times more carbohydrate uptake and drug efflux systems, and 3 times more lipid transporters. Bba also has polyamine and carboxylate transporters lacking in Bex. Bba has more than twice as many members of the Mot-Exb family of energizers, but both may have energizers for gliding motility. They use entirely different types of systems for iron acquisition. Both contain unexpectedly large numbers of pseudogenes and incomplete systems, suggesting that they are undergoing genome size reduction. Interestingly, all 5 outer-membrane receptors in Bba are lacking in Bex. The 2 organisms have similar numbers and types of peptide and amino acid uptake systems as well as protein and carbohydrate secretion systems. The differences observed correlate with and may account, in part, for the different lifestyles of these 2 bacterial predators.

The ImpX transporters of the drug/metabolite transporter superfamily were first proposed to transport riboflavin (RF; vitamin B2) based on findings of a cis-regulatory RNA element responding to flavin mononucleotide (an FMN riboswitch). Bdellovibrio exovorous JSS has a homolog belonging to this superfamily. It has 10 TMSs and shows 30% identity to the previously characterized ImpX transporter from Fusobacterium nucleatum. However, the ImpX homolog is not regulated by an FMN-riboswitch. In order to test the putative function of the ImpX homolog from B. exovorous (BexImpX), we cloned and heterologously expressed its gene. We used functional complementation, growth inhibition experiments, direct uptake experiments and inhibition studies, suggesting a high degree of specificity for RF uptake. The EC50 for growth with RF was estimated to be in the range 0.5-1 µM, estimated from the half-maximal RF concentration supporting the growth of a RF auxotrophic Escherichia coli strain, but the K half for RF uptake was 20 µM. Transport experiments suggested that the energy source is the proton motive force but that NaCl stimulates uptake. Thus, members of the ImpX family members are capable of RF uptake, not only in RF prototrophic species such as F. nucleatum, but also in the B2 auxotrophic species, B. exovorous.

No abstract

Background and Objectives: Oxalate degrading bacteria and herbal extracts are new strategy for reducing hyperoxaluria. In Iranian traditional medicine, Sankol oral drop is widely used as an antispasmodic drug to reduce stones from urinary tract. This study aimed to evaluate the synergistic effect of oxalate-degrading bacteria and Sankol oral drop in reducing urinary oxalate in rat model. Materials and Methods: Several bacterial strains, including Lactobacillus (4), Bifidobacterium (2) and L. paracasei (2) (very strong in degrading oxalate in vitro) were used in this study. Male Wistar rats were divided into 6 groups (n = 6). The rats of Group I received normal diet and drinking water + 60% ethanol (positive group). Groups II (negative group), III, IV, V, and VI rats received diet containing ethylene glycol (3%) for 30 days. Groups III rats received Sankol with minimum concentration (7.5 ml/kg/b.w), Group IV rats received Sankol with maximum concentration (9 ml/kg/b.w), Group V rats received Sankol with minimum concentration + probiotic, and Group VI rats received Sankol with maximum concentration + probiotic for 30 days. Results: Treatment with Sankol (maximum concentration) and oxalate-degrading probiotic bacteria significantly reduced urinary oxalate (P = .0001). At the end of treatment period, rats in groups II (negative control) showed a high score of CaOx crystal, while rats in VI groups did not show any CaOx crystal. Conclusion: This is the first study on the simultaneous use of Sankol herbal drop and oxalate-degrading probiotic bacteria that showed a significant reduction in urinary oxalate.