Point Mutations in TbpA Abrogate Human Transferrin Binding in Neisseria gonorrhoeae

TonB-dependent transporters (TDTs) are essential proteins for metal acquisition, an important step in the growth and pathogenesis of many pathogens, including Neisseria gonorrhoeae, the causative agent of gonorrhea. There is currently no available vaccine for gonorrhea; TDTs are being investigated as vaccine candidates because they are highly conserved and expressed in vivo. Transferrin binding protein A (TbpA) is an essential virulence factor in the initiation of experimental infection in human males and functions by acquiring iron upon binding to host transferrin (human transferrin [hTf]). The loop 3 helix (L3H) is a helix finger that inserts into the hTf C-lobe and is required for hTf binding and subsequent iron acquisition. This study identified and characterized the first TbpA single-point substitutions resulting in significantly decreased hTf binding and iron acquisition, suggesting that the helix structure is more important than charge for hTf binding and utilization. The tbpA D355P ΔtbpB and tbpA A356P ΔtbpB mutants demonstrated significantly reduced hTf binding and impaired iron uptake from Fe-loaded hTf; however, only the tbpA A356P ΔtbpB mutant was able to grow when hTf was the sole source of iron. The expression of tbpB was able to restore function in all tbpA mutants. These results implicate both D355 and A356 in the key binding, extraction, and uptake functions of gonococcal TbpA.

Structural Basis for Evasion of Nutritional Immunity by the Pathogenic Neisseriae

The pathogenic Neisseria species are human-adapted pathogens that cause quite distinct diseases. Neisseria gonorrhoeae causes the common sexually transmitted infection gonorrhea, while Neisseria meningitidis causes a potentially lethal form of bacterial meningitis. During infection, both pathogens deploy a number of virulence factors in order to thrive in the host. The focus of this review is on the outer membrane transport systems that enable the Neisseriae to utilize host-specific nutrients, including metal-binding proteins such as transferrin and calprotectin. Because acquisition of these critical metals is essential for growth and survival, understanding the structures of receptor-ligand complexes may be an important step in developing preventative or therapeutic strategies focused on thwarting these pathogens. Much can also be learned by comparing structures with antigenic diversity among the transporter sequences, as conserved functional domains in these essential transporters could represent the pathogens' "Achilles heel." Toward this goal, we present known or modeled structures for the transport systems produced by the pathogenic Neisseria species, overlapped with sequence diversity derived by comparing hundreds of neisserial protein sequences. Given the concerning increase in N. gonorrhoeae incidence and antibiotic resistance, these outer membrane transport systems appear to be excellent targets for new therapies and preventative vaccines.

Antibiotic activity and microbial community of the temperate sponge, Haliclona sp

AIMS

Sessile marine invertebrates engage in a diverse array of beneficial interactions with bacterial symbionts. One feature of some of these relationships is the presence of bioactive natural products that can defend the holobiont from predation, competition or disease. In this study, we investigated the antimicrobial activity and microbial community of a common temperate sponge from coastal North Carolina.

METHODS AND RESULTS

The sponge was identified as a member of the genus Haliclona, a prolific source of bioactive natural products, based on its 18S rRNA gene sequence. The crude chemical extract and methanol partition had broad activity against the assayed Gram-negative and Gram-positive pathogenic bacteria. Further fractionation resulted in two groups of compounds with differing antimicrobial activity, primarily against Gram-positive test organisms. There was, however, notable activity against the Gram-negative marine pathogen, Vibrio parahaemolyticus. Microbial community analysis of the sponge and surrounding sea water via denaturing gradient gel electrophoresis (DGGE) indicates that it harbours a distinct group of bacterial associates.

CONCLUSIONS

The common temperate sponge, Haliclona sp., is a source of multiple antimicrobial compounds and has some consistent microbial community members that may play a role in secondary metabolite production.

SIGNIFICANCE AND IMPACT OF THE STUDY

These data suggest that common temperate sponges can be a source of bioactive chemical and microbial diversity. Further studies may reveal the importance of the microbial associates to the sponge and natural product biosynthesis.

The Holistic Living Inventory: correlations with MMPI

Scores on the Holistic Living Inventory were correlated with MMPI scores for 129 college students. The results support validity for the Holistic Living Inventory.

A comparison of muscle relaxation training and music in the reduction of state and trait anxiety

A comparison was made between muscle-relaxation training and relaxing music in the reduction of state and trait anxiety. Ss were 108 anxious female college students, half of whom received three sessions in muscle-relaxation training and half of whom received three sessions of relaxing music. Results indicate that both types of treatment significantly reduce state anxiety, but neither reduces trait anxiety. Results support Spielberger's state-trait anxiety theory and hold some implication for treatment.