Bacterial Attachment, Aggregation, and Alignment on Subcellular Nanogratings

Abstract

Recent investigations on the interactions of bacteria with micro/nanostructures have revealed a wide range of prokaryotic responses that were previously unknown. Despite these advances, however, it remains unclear how collective bacterial behavior on a surface would be influenced by the presence of anisotropic nanostructures with subcellular dimensions. To clarify this, the attachment, aggregation, and alignment of Pseudomonas aeruginosa on orderly subcellular nanogratings with systematically varied geometries were investigated. Compared with a flat surface, attachment and aggregation of bacteria on the nanogratings were reduced by up to 83 and 84% respectively, whereas alignment increased by a maximum of 850%. Using a semiempirical quantitative model, these results were shown to be caused by a lowering of physicochemical attraction between the substrate and bacteria, possible disruption to cell communication, and physical isolation of bacteria that were entrenched in the nanogratings by capillary action. Furthermore, the bacterial attachment level was generally found to be exponentially related to the contact area between the substrate and bacterial cells, except when there were significant deficits in the available contact area, which prompted the bacterial cells to employ their appendages to maintain a minimum attachment rate. Because the contact area for adhesion is strongly dependent on the geometry of the surface features and orientation of the bacterial cells, these results indicate that the conventional practice of using roughness parameters to draw quantitative relationships between surface topographies and bacterial attachment could suffer from inaccuracies due to the lack of shape and orientation information provided by these parameters. On the basis of these insights, design principles for generating maximal and minimal bacterial attachment on a surface were also proposed and verified with results reported in the literature.

Micro- and Nanotopography Sensitive Bacterial Attachment Mechanisms: A Review

“…The features on these surfaces seemed able to direct cell patterning independent of the expression of appendages by the cells (Hochbaum and Aizenberg, 2010). The interstitial space between surface features (Epstein et al, 2011) and the depth of the features (Lai, 2018) were both found to be critical for bacterial cell patterning. For example, aggregation of P. aeruginosa cells on Si nanogratings was reduced to 20% of that on flat controls, because the cells were entrapped to the bottom of the Si nanogratings deeper than 500 nm, and consequently became unavailable for forming cell clusters (Lai, 2018).…”

“…The interstitial space between surface features (Epstein et al, 2011) and the depth of the features (Lai, 2018) were both found to be critical for bacterial cell patterning. For example, aggregation of P. aeruginosa cells on Si nanogratings was reduced to 20% of that on flat controls, because the cells were entrapped to the bottom of the Si nanogratings deeper than 500 nm, and consequently became unavailable for forming cell clusters (Lai, 2018). The patterning and ordering of early colonizers can interfere with natural biofilm development and organization (Hochbaum and Aizenberg, 2010), as some bacteria rely on contact-dependent signaling cascades to achieve cooperative communal functions (Blango and Mulvey, 2009).…”

Bacterial nanotubes mediate bacterial growth on periodic nano-pillars

“…Hochbaum et al 4 found that P. aeruginosa PA14 tended to maximum their contact area with the surface, forming a spontaneous cell alignment between periodic nanopillars with a post pitch of 2.2, 0.9 and 0.7 mm. Subsequent work showed similar behaviour as P. aeruginosa aligned within subcellular-nanogratings, 13 Escherichia coli orientated towards surface line patterns, 14 and Pseudomonas fluorescens were trapped preferentially in surface trenches. 15 As such, topographical features with micrometre or submicrometer length scales (i.e., comparable with the length scale of the bacteria themselves) can influence the arrangement of adhered cells during the early stage of biofilm development.…”

“…Our investigations above indicated that cell alignment may be a general phenomenon, occurring in examples of wild-type bacteria and in the absence of flagella or pili, which was also consistent with the findings in other studies. 4,13 Overall, the investigation above showed that the surface topography at the micro-and nanoscale that is comparable to the bacterial size, can affect bacterial alignment and attachment. It is likely that cells try to maximize contact area with the surface topography, presumably to achieve a stronger and more stable attachment, which results in a specific alignment behaviour of the attached cells.…”

“…15 As such, topographical features with micrometre or submicrometer length scales (i.e., comparable with the length scale of the bacteria themselves) can influence the arrangement of adhered cells during the early stage of biofilm development. 4,16,17 However, the underlying mechanism that results in the observed arrangements of cells is currently unclear, 4,13,14 which hinders the development of an overarching understanding of bacterial cell-material interactions.…”