Whole-cell and periplasmic protein banding patterns of environmental and human Bacteroides fragilis strains

Bacterial Whole Cell Protein Profiling: Methodology, Applications and Constraints

Background:

In the era of modern microbiology, several methods are available for identification and typing of bacteria, including whole genome sequencing. However, in microbiological laboratories or hospitals where genomic based molecular typing methods and/or trained manpower are unavailable, whole cell protein profiling using sodium dodecyl sulfate polyacrylamide gel electrophoresis might be a useful alternative/supplementary method for bacterial identification, strain typing and epidemiology. Whole cell protein profiling by SDS-PAGE is based on the principle that under standard growth conditions, a bacterial strain expresses the same set of proteins, the pattern of which can be used for bacterial identification.

Objective:

The objective of this review is to assess the current status of whole cell protein profiling by SDS-PAGE and its advantages and constraints for bacterial identification and typing.

Results and Conclusions:

Several earlier and recent studies prove the potential and utility of this technique as an adjunct or supplementary method for bacterial identification, strain typing and epidemiology. There is no denying the fact that utility of this technique as an adjunct or supplementary method for bacterial identification and typing has already been demonstrated and its practical applications need to be evaluated further.

Binding and degradation of fibrinogen by Bacteroides fragilis and characterization of a 54 kDa fibrinogen-binding protein

Bacteroides fragilis is a bacterium that resides in the normal human gastro-intestinal tract; however, it is also the most commonly isolated Gram-negative obligate anaerobe from human clinical infections, such as intra-abdominal abscesses, and the most common cause of anaerobic bacteraemia. Abscess formation is important in bacterial containment, limiting dissemination of infection and bacteraemia. In this study, we investigated B. fragilis binding and degradation of human fibrinogen, the major structural component involved in fibrin abscess formation. We have shown that B. fragilis NCTC9343 binds human fibrinogen. A putative Bacteroides fragilis fibrinogen-binding protein, designated BF-FBP, identified in the genome sequence of NCTC9343, was cloned and expressed in Escherichia coli. The purified recombinant BF-FBP bound primarily to the human fibrinogen Bbeta-chain. In addition, we have identified fibrinogenolytic activity in B. fragilis exponential phase culture supernatants, associated with fibrinogenolytic metalloproteases in NCTC9343 and 638R, and cysteine protease activity in YCH46. All nine clinical isolates of B. fragilis examined degraded human fibrinogen; with eight isolates, initial Aalpha-chain degradation was observed, with varying Bbeta-chain and gamma-chain degradation. With one blood culture isolate, Bbeta-chain and gamma-chain degradation occurred first, followed by subsequent Aalpha-chain degradation. Our data raise the possibility that the fibrinogen-binding protein of B. fragilis, along with a variety of fibrinogenolytic proteases, may be an important virulence factor that facilitates dissemination of infection via reduction or inhibition of abscess formation.

The use of SDS polyacrylamide gel electrophoresis of periplasmic proteins to subtype Pseudomonas aeruginosa pyocin type 10/b clinical isolates

The periplasmic protein banding patterns (PPBPs) of thirteen strains of Pseudomonas aeruginosa pyocin type 10/b implicated in two nosocomial outbreaks in the neonatal unit of Rafeidia Hospital, Nablus, Palestine, were examined. In addition, five strains from sporadic cases from the same unit occurring in 1996 and 1997 were also studied. Despite different sources of the strains, PPBPs generated by PAGE suggested a clonal nature of the strains obtained during each of the two outbreaks. Although they had very similar PPBPs, the two outbreak clones were not identical. In contrast, sporadic strains of P. aeruginosa pyocin type 10 appeared to be much more heterogeneous than those of the two outbreaks. PPBP analysis appeared to be a useful tool that may be of value for epidemiological purposes.