Novel combination of atomic force microscopy and epifluorescence microscopy for visualization of leaching bacteria on pyrite.

Bioleaching of metal sulfides is an interfacial process comprising the interactions of attached bacterial cells and bacterial extracellular polymeric substances with the surface of a mineral sulfide. Such processes and the associated biofilms can be investigated at high spatial resolution using atomic force microscopy (AFM). Therefore, we visualized biofilms of the meso-acidophilic leaching bacterium Acidithiobacillus ferrooxidans strain A2 on the metal sulfide pyrite with a newly developed combination of AFM with epifluorescence microscopy (EFM). This novel system allowed the imaging of the same sample location with both instruments. The pyrite sample, as fixed on a shuttle stage, was transferred between AFM and EFM devices. By staining the bacterial DNA with a specific fluorescence dye, bacterial cells were labeled and could easily be distinguished from other topographic features occurring in the AFM image. AFM scanning in liquid caused deformation and detachment of cells, but scanning in air had no effect on cell integrity. In summary, we successfully demonstrate that the new microscopic system was applicable for visualizing bioleaching samples. Moreover, the combination of AFM and EFM in general seems to be a powerful tool for investigations of biofilms on opaque materials and will help to advance our knowledge of biological interfacial processes. In principle, the shuttle stage can be transferred to additional instruments, and combinations of AFM and EFM with other surface-analyzing devices can be proposed.

Cardiovascular responses during thermoneutral, head-out water immersion in patients with coronary artery disease.

PURPOSE: Water is frequently recommended as a therapeutic medium for cardiac patients. Reports on the cardiovascular response to immersion often differ, however, depending, for instance, if full or partial immersion were considered. The purpose of this study was to examine the cardiovascular responses to 2 immersion protocols in 3 age and gender-matched groups of patients each with a specific coronary artery disease. METHODS: Fifteen patients with coronary artery disease entered water using a stepwise immersion (STEP) protocol (5 stages in 15 minutes) and an immediate, complete immersion (IM) protocol (2 stages in 6 minutes). Cardiac indices were monitored by transthoracic echocardiography. The heart rate was generated from the electrocardiogram, and blood pressure was measured using a manual mercury manometer. RESULTS: The end-diastolic volume, end-systolic volume, stroke volume, and cardiac output decreased during STEP but increased during IM. As a consequence, the preload on the heart was greater during IM. Changes in systolic blood pressure were comparable in the 2 situations. The immersion-related decrease of heart rate was seen during STEP, but not during IM. Nevertheless, the hemodynamic responses to the initial stages of STEP up to the ankle joint were quite similar to those observed during immediate immersion to the neck. CONCLUSION: The cardiovascular responses to IM and STEP differed between protocols and even among subgroups within the same protocol. The findings further suggest that isolated immersion of body extremities can be beneficial to patients with coronary artery disease as preliminary preparation before complete water immersion is undertaken.