How to speed up the detection of aerobic microbial contaminations by using isothermal microcalorimetry

Journal of Thermal Analysis and Calorimetry - A sudden expansion is a classical problem which is happened in different industries such as energy conversion, environmental control, and chemical...     

Photosynthetic energy conversion in the diatom <Emphasis Type="Italic">Phaeodactylum tricornutum</Emphasis>

Isothermal microcalorimetry can be used to investigate the photosynthetic energy conversion of autotrophic organisms. In this study, for the first time a diatom alga was used to compare the calorimetrically measured heat flux with measurements of the photosynthetic performance by oxygen evolution and pulse-amplitude modulated fluorescence. The presented experimental setup proved suitable to compare calorimetric data with those of conventional methods of the determination of photosynthesis rates. Special attention was paid to the contribution of energy dissipation via non-photochemical quenching (NPQ) of chlorophyll fluorescence to the metabolic energy balance. This was achieved by a combination of different light conditions and the use of an inhibitor of NPQ. Although NPQ is an important photoprotective mechanism in diatoms, the inhibition of NPQ resulted in an activation of alternative, energy dissipating pathways for absorbed radiation which completely compensated for the fraction of energy dissipation by NPQ.     

Chip-calorimetric monitoring of biofilm eradication with bacteriophages reveals an unexpected infection-related heat profile

Bacteriophages or phage-derived biological structures are a promising alternative to the application of antibiotics to eradicate biofilms. These countermeasures are highly cell specific. For a better understanding of the sequence of the underlying processes (attachment, infection, multiplication, phage release), for optimization of phage applications, or simply for screening of suitable phages or phage-derived enzymes, real-time monitoring devices are urgently required. Calorimetry is promising because it is non-invasive and quantitatively connected to the metabolic fluxes. Chip-calorimetry provides real-time information about biofilm eradication by phages. This was confirmed by comparison with reference analyses (i.e., confocal laser scanning microscopy, colony plate counts, or phage titre determination). Furthermore, chip-calorimetry provides additional information which was not captured by the reference methods such as the enhanced cell-specific heat production caused by the infection process and a residual activity of seemingly persistent bacteria.     

Highly sensitive determination of ectoine and other compatible solutes by anion-exchange chromatography and pulsed amperometric detection

In saline media prokaryotes compensate for the osmotic pressure of the surrounding medium by producing osmolytes. Although these osmolytes or osmoprotectors have quite diverse structures, most of them can be determined by anion-exchange chromatography combined with integrated pulsed amperometric detection. This technique offers the advantages of very high sensitivity and new opportunities to determine ectoine and 5-hydroxyectoine—two important osmolytes —after hydrolytic cleavage of the pyrimidine ring. It can even be used to screen bacterial colonies on agar for compatible solutes. Furthermore, it allows amino acids and osmolytes of this type to be determined without derivatization. To test the method we applied it to two halotolerant bacterial strains: Stenotrophomonas rhizophila DSM 14405^T and Halomonas elongata DSM 2581^T. The first strain produced trehalose and glucosylglycerol, and the second ectoine, as the main osmotic counterweight. The relationship between the content of these osmolytes in the bacterial biomass and the external salinity is described.     

Studying the toxic effect of cadmium and hexavalent chromium on microbial activity of a soil and pure microbe

Using TAM III multi-channel calorimetry combined with direct microorganism counting (bacteria, actinomycetes and fungi) under laboratory conditions, we determined the microbial population count, resistance and activity toward cadmium (Cd(II)) and hexavalent chromium (Cr(VI)) toxicity in soil. The thermokinetic parameters, which can represent soil microbial activity, were calculated from power-time curves of soil microbial activity obtained by microcalorimetric measurement. Simultaneous application of the two methods showed that growth rate constant (k), peak-heat output power (P _max) and the number of living microorganisms decreased with increasing concentration of Cd and Cr. The accumulation of Cr on E. coli was conducted by HPLC-ICP-MS. Cr⁶⁺ accumulation by Escherichia coli was increased steadily with increasing Cr⁶⁺ concentration. The results revealed that the change in some thermo-kinetic parameters could have good corresponding relationship with metal accumulation. Our work also suggests that microcalorimetry is a fast, simple, more sensitive, on-line and in vitro method that can be easily performed to study the toxicity of different species of heavy metals on microorganism compared to other biological methods, and can combine with other analytic methods to study the interaction mechanism between environmental toxicants and microbes.