Comparative endoscopic and SEM analyses and imaging for biofilm growth on porous quartz sand

Abstract

The paper presents an endoscope technique to provide a non-destructive detection and imaging of biofilms on porous sand grains without disturbing the system. This in situ observation of biofilm growth was carried out by inserting an endoscope into the reactor after introducing the substrate into a water-saturated quartz sand-packed reactor. As the microbes grew on the media surface with time, an expansion was presented in biofilm area. In this way, the growth of biofilm on porous sand grains could be continuously captured. The expanding of the biofilm image was observed, and the biofilm on the sand grains was measured by image analysis of biofilm crosssections. In order to further identify the biofilm growth, at the end of experiment the packed reactor was dismantled and biofilms along with the aquifer material were sampled for the biofilm growth observation by the scanning electron microscopy (SEM). The biofilm thickness was also measured by image analysis of biofilm cross-sections. The results demonstrated significant spatial variations in mean biofilm thickness (106.2 ± 12.54 lm to 243.5 ± 26.53 lm) and thickness variability (0.07-0.12) using image analysis of SEM. However, the mean biofilm thickness measurements done by image analysis of SEM were about 60-82% smaller compared with those by image analysis of endoscopy. This is because of the dehydration and alteration of the biofilm material after dismantling the reactor for SEM observations. In comparison, we found that the endoscope image could provide a first-hand observation of biofilm growth without disrupting the system, while the SEM image could give a better resolution.

Mimicking biofilm formation and development: Recent progress in in vitro and in vivo biofilm models

“…Here, bacterial microcolonies spread out forming larger aggregates that are referred to as “macrocolonies” or “towers” ( Gupta et al., 2016 ; Ha and O'Toole, 2015 ), causing the biofilm to thicken ( Figure 6 ). Biofilm thickness is variable depending on the species, substrate, time required for maturation, microenvironment conditions such as nutrient availability and shear flow, as well as the methods applied for its determination ( Heydorn et al., 2000a ; Heydorn et al., 2000b ; Janakiraman et al., 2009 ; Jean et al., 2004 ; Meyer et al., 2011 ; Suarez et al., 2019 ). Most biofilms are found to be multispecies, where each microorganism influences the morphology and architecture of the resulting biofilm; which may be different from monospecies biofilms.…”

Monitoring of Wild Pseudomonas Biofilm Strain Conditions Using Statistical Characterization of Scanning Electron Microscopy Images

“…In contemporary research, several methods of biofilm characterisation using statistical techniques has been reported on 2D SEM images [42][43][44][45][46][47][48] . Yang et al 49 and Jackson et al 50 have studied several textural features of microscope images, e.g.…”

“…This section, briefly reviews the contributions previously made in existing literature on biofilm quantification using various imaging techniques through different physical or chemical features, as well as previous works on mathematical modeling of biofilm growth. In contemporary research, several methods of biofilm characterization using statistical techniques has been reported on two-dimensional (2D) scanning electron microscopy (SEM) images. − Yang et al and Jackson et al have studied several textural features of microscope images, e.g. entropy, angular second moment, inverse difference moment, as well as morphological features, e.g.…”

Mathematical Models of Mass Transfer in Tissue for Molecular Medicine with Reversible Electroporation

“…Electron microscopy techniques such as SEM and TEM have been used to estimate the thickness of biofilms on surfaces (Vandevivere and Baveye 1992b;Rinck-Pfeiffer et al 2000;Hand et al 2008), however, they cannot be applied directly to porous media systems and can therefore suffer artifacts due to destructive sampling, sample preparation, and the vacuum conditions necessary for the analysis (Nam et al 2000). For instance, in one study, the mean biofilm thickness estimates based on SEM images were about 60%-82% less than those obtained through optical microscopy (Jean et al 2004). Environmental scanning electron microscopy (ESEM) can avoid some of the artifacts possibly introduced during sample preparation and imaging compared to SEM.…”