FTIR as an easy and fast analytical approach to follow up microbial growth during fungal pretreatment of poplar wood with Phanerochaete chrysosporium.

Since the determination of the fermentation kinetics is one of the main challenges in solid state fermentation, the quantitative measurement of biomass growth during microbial pretreatment by FTIR spectroscopy in Attenuated Total Reflectance mode was evaluated. Peaks at wave numbers of 1651 cm-1 and 1593 cm-1 showed to be affected during pretreatment of poplar wood particles by Phanerochaete chrysosporium MUCL 19343. Samples with different microbial biomass fractions were obtained from two different experiments, i.e., shake flask and fixed-bed reactor experiments. The glucosamine concentration was compared to the normalized absorbance ratio of the 1651 cm-1 to 1593 cm-1 peak, measured by FTIR-ATR, and resulted in a linear relationship. The application of a normalized absorbance ratio in function of time provided a graph that was similar to the microbial growth curve. Application of FTIR in ATR mode to follow-up kinetics during solid state fermentation seems to be a fast and easy alternative to laborious measurement techniques, such as glucosamine determination.

HPV16 genetic variation and the development of cervical cancer worldwide.

BACKGROUND: Factors that favour a small proportion of HPV16 infections to progress to cancer are still poorly understood, but several studies have implicated a role of HPV16 genetic variation. METHODS: To evaluate the association between HPV16 genetic variants and cervical cancer risk, we designed a multicentre case-control study based on HPV16-positive cervical samples (1121 cervical cancer cases and 400 controls) from the International Agency for Research on Cancer biobank. By sequencing the E6 gene, HPV16 isolates were classified into variant lineages and the European (EUR)-lineage isolates were subclassified by the common polymorphism T350G. RESULTS: Incidence of variant lineages differed between cases and controls in Europe/Central Asia (P=0.006, driven by an underrepresentation of African lineages in cases), and South/Central America (P=0.056, driven by an overrepresentation of Asian American/North American lineages in cases). EUR-350G isolates were significantly underrepresented in cervical cancer in East Asia (odds ratio (OR)=0.02 vs EUR-350T; 95% confidence interval (CI)=0.00-0.37) and Europe/Central Asia (OR=0.42; 95% CI=0.27-0.64), whereas the opposite was true in South/Central America (OR=4.69; 95% CI=2.07-10.66). CONCLUSION: We observed that the distribution of HPV16 variants worldwide, and their relative risks for cervical cancer appear to be population-dependent.

Heat stress adaptation of Escherichia coli under dynamic conditions: effect of inoculum size.

AIMS: When subjected to dynamic temperatures surpassing the expected maximum growth temperature, Escherichia coli K12 MG1655 shows disturbed growth curves. These irregular population dynamics were explained by considering two subpopulations, i.e. a thermoresistant and a thermosensitive one (Van Derlinden et al. 2010a). In this paper, the influence of the initial cell concentration on the subpopulations' dynamics is evaluated. METHODS AND RESULTS: Experiments were performed in a bioreactor with the temperature increasing from 42 to 65.2 °C (1 and 4 °C h(-1)) with varying initial cell concentrations [6, 12 and 18 ln(CFU ml(-1))]. When started from the highest cell concentration, the population was characterized by a higher overall maximum growth temperature and a higher inactivation temperature. For all experimental set-ups, resistant cells were still growing at the final temperature of 65.2 °C. CONCLUSIONS: The initial cell concentration had no effect on temperature resistance. The increase in temperature resistance of the sensitive subpopulation was because of the change of the physiological state to the stationary phase. SIGNIFICANCE AND IMPACT OF THE STUDY: A higher initial cell concentration leads to higher heat stress adaptation when cultures reach a maximum cell concentration. The observed growth at a temperature of 65.2 °C is very important for food safety and the temperature treatment of micro-organisms.