Objective: Mitochondrial dysfunction and oxidative stress in insulin responsive tissues is implicated in the pathogenesis of type 2 diabetes. Whether these perturbations extend to other tissues and contribute to their pathophysiology is less well established. The objective of this study was to investigate platelet mitochondria to evaluate whether type 2 diabetes associated mitochondrial dysfunction is evident in circulating cells. Method: A pilot study of mitochondrial respiratory function and proteomic changes comparing platelets extracted from insulin sensitive (n=8) and type 2 diabetic subjects (n=7). Results: In-situ platelet mitochondria show diminished oxygen consumption and lower oxygen-dependent ATP synthesis in diabetic versus control subjects. Mass spectrometric identification and confirmatory immunoblot analysis identifies induction of the mitochondrial anti-oxidant enzymes superoxide dismutase 2 and thioredoxin-dependent peroxide reductase 3 in platelets of diabetic subjects. As oxidative stress upregulates anti-oxidant enzymes we assessed mitochondrial protein carbonylation as an index of oxidative-stress. Platelets of diabetic subjects exhibit significantly increased protein carbonylation compared to controls. Conclusions: As platelets are anuclear fragments of megakaryocytes, our data suggest that the bone marrow compartment in type 2 diabetic subjects is exposed to increased mitochondrial oxidative stress with upregulation of nuclear-encoded antioxidant mitochondrial enzymes. This ‘stress-signature’ in platelets of diabetic subjects is associated with a diminution of their mitochondrial contribution to energy production and support that mitochondrial perturbations in type 2 diabetes extends beyond the classical insulin responsive tissues. Platelets, as “accessible human tissue”, may be useful to measure the mitochondrial modulatory effects of emerging anti-diabetic therapeutics.

e Streptococcus gordonii is a commensal species of human oral flora. It initiates dental biofilm formation and provides binding sites for later colonizers to attach to and generate mature biofilm. Smoking is the second highest risk factor for periodontal disease, and cigarette smoke extract has been reported to facilitate Porphyromonas gingivalis-S. gordonii dual-species biofilm formation. Our hypothesis is that nicotine, one of the most important and active components of tobacco, stimulates S. gordonii multiplication and aggregation. In the present study, S. gordonii planktonic cell growth (kinetic absorbance and CFU), biofilm formation (crystal violet stain and confocal laser scanning microscopy [CLSM]), aggregation with/without sucrose, and 11 genes that encode binding proteins or regulators of gene expression were investigated. Results demonstrated planktonic cell growth was stimulated by 1 to 4 mg/ml nicotine treatment. Biofilm formation was increased at 0.5 to 4 mg/ml nicotine. CLSM indicated bacterial cell mass was increased by 2 and 4 mg/ml nicotine, but biofilm extracellular polysaccharide was not significantly affected by nicotine. Cell aggregation was upregulated by 4, 8, and 16 mg/ml nicotine with sucrose and by 16 mg/ml nicotine without sucrose. Quantitative reverse transcriptase PCR indicated S. gordonii abpA, scaA, ccpA, and srtA were upregulated in planktonic cells by 2 mg/ml nicotine. In conclusion, nicotine stimulates S. gordonii planktonic cell growth, biofilm formation, aggregation, and gene expression of binding proteins. Those effects may promote later pathogen attachment to tooth surfaces, the accumulation of tooth calculus, and the development of periodontal disease in cigarette smokers.

As an indispensable virulence determinant, Salmonella pathogenicity island 1(SPI-1) has gained much attention in host-pathogen interactions. More and more studies on SPI-1 have demonstrated that it is far more complex than the one we used to expect. It not only affects sophisticated activities during infection, including invasion, replication, and host responses, but also extends to other fields like biofilm formation. In addition, mutants in SPI-1 effectors have been explored as vaccines, the effective ways to prevent salmonellosis. The activity of SPI-1 is influenced by many factors which have been widely reported. Investigations on these factors may provide new insights into prevention and treatment of salmonellosis. Therefore, SPI-1 is a tempting issue worthy of further exploration. In this review, we will probe into SPI-1 systematically.

Streptococcus mutans is a common Gram-positive bacterium and plays a significant role in dental caries. Tobacco and/or nicotine have documented effects on S. mutans growth and colonization. Sortase A is used by many Gram-positive bacteria, including S. mutans, to facilitate the insertion of certain cell surface proteins, containing an LPXTGX motif such as antigen I/II. This study examined the effect of nicotine on the function of sortase A to control the physiology and growth of S. mutans using wild-type S. mutans NG8, and its isogenic sortase-defective and -complemented strains. Briefly, the strains were treated with increasing amounts of nicotine in planktonic growth, biofilm metabolism, and sucrose-induced and saliva-induced antigen I/II-dependent biofilm formation assays. The strains exhibited no significant differences with different concentrations of nicotine in planktonic growth assays. However, they had significantly increased (P≤0.05) biofilm metabolic activity (2- to 3-fold increase) as the concentration of nicotine increased. Furthermore, the sortase-defective strain was more sensitive metabolically to nicotine than the wild-type or sortase-complemented strains. All strains had significantly increased sucrose-induced biofilm formation (2- to 3-fold increase) as a result of increasing concentrations of nicotine. However, the sortase-defective strain was not able to make as much sucrose- and saliva-induced biofilm as the wild-type NG8 did with increasing nicotine concentrations. These results indicated that nicotine increased metabolic activity and sucrose-induced biofilm formation. The saliva-induced biofilm formation assay and qPCR data suggested that antigen I/II was upregulated with nicotine but biofilm was not able to be formed as much as wild-type NG8 without functional sortase A.

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Extracellular DNA (eDNA) was identified and characterized in a 2-day-old biofilms developed by Salmonella enterica ser. Typhimurium SR-11 and S. enterica ser. Typhi ST6 using confocal laser scanning microscopy (CLSM) and enzymatic extraction methods. Results of microtitre plate assay and CLSM analysis showed both Salmonella strains formed significantly more biofilms in the presence of DNase I; Furthermore, a remarkable decrease of biofilm formation was observed when eDNA was added in the inoculation. However, for the pre-established biofilms on polystyrene and glass, no significant difference was observed between the DNase I treated biofilm and the corresponding non-treated controls. In conclusion, these results demonstrate that eDNA is a novel matrix component of Salmonella biofilms. This is the first evidence for the presence of eDNA and its inhibitive and destabilizing effect during biofilm development of S. enterica ser. Typhimurium and S. enterica ser. Typhi on abiotic surfaces.

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