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Acclimation and flexible response mechanisms are survival adaptations allowing prokaryotic cells to colonize diverse habitats and maintain viability in nature. Lack of water significantly impacts cellular response, which can be partially compensated for through community interactions and accessing survival means beyond the cell's boundaries. In the present study, higher numbers of cultivable Gram-positive Arthrobacter sp. and Gram-negative Pseudomonas stutzeri cells were found on surfaces when high population density was used after prolonged periods of desiccation and nutrient starvation. Total cell counts during desiccation periods decreased slower than culturable cell counts independently from initial population density. The presence of homogenate, prepared by filtering homogenized cultures through a 0.2 µm filter, extended culturability of Arthrobacter sp. cells, while intact heat-killed cells extended the culturability of Arthrobacter sp. and P. stutzeri. Our results suggest very slow cell membrane breakdown for desiccated bacterial cells at solid-air interfaces over extended time spans, which may serve as reservoirs of nutrients, and may potentially provide trace amounts of water for surviving cells. Higher initial population density and recycling of resources from "zombie"-like cells, may support growth in a similar fashion as access to cell lysates or the contents of heat-killed cells analogous to dead-phase cultures where some cells experience cryptic growth. [Display omitted] [ABSTRACT FROM AUTHOR]

Effective removal of prokaryotic cells from clay interfaces such as bentonite is essential for quantitative assessment of microbial communities, considering that strong bentonite clay-DNA and –RNA complexes challenge the use of molecular-based techniques. In this study, aerobic bacteria were isolated from Wyoming MX-80 bentonite and sequenced for identification (16S rRNA). A glass-bentonite substrate and sterile bentonite powder were inoculated with Arthrobacter sp. (isolated from bentonite) to test cell removal efficiency using sonication and vortexing. Manipulation of pH (pH 7 versus pH 9) did not affect cell removal efficiency, while changes in temperature within limits (15–37 °C) did affect cell removal efficiency. To evaluate microbial survival during desiccation, bacterial isolates were inoculated onto glass and bentonite-covered glass coverslip substrates, and particulate bentonite. Substrates were desiccated, and cells were removed by vortexing at different time points over 31 days. Abundance of viable cells followed a first-order rate of decrease. Vegetative desiccation-tolerant Arthrobacter sp. isolates from bentonite clay had lower loss of viable, culturable cells (0.07 d−1 to 0.89 d−1) than did a Bacillus sp. isolate (>1 d−1) or a Pseudomonas stutzeri isolate (0.79 to >1 d−1), suggesting Arthrobacter sp. may be more tolerant of these prolonged periods of desiccation on the bentonite-air interface. Tolerance to matric stress by microorganisms varies depending on the cellular adaptation of the target species, the physical and chemical properties of the given solid-air environment, as well as the employed population and community-based survival mechanisms. • Factors affecting attachment of bacteria to clay are considered with the aim of improving cell removal strategies • Sonication and vortexing are effective for removal of bacterial cells from bentonite clay-air interfaces • Bacterial survival at the solid-air interface of clay can be described using a first-order loss model • Bacterial species demonstrated variability in long-term survival at solid-air interfaces • Tolerance to matric stress goes beyond cellular adaptation, to population and community-based survival mechanisms [ABSTRACT FROM AUTHOR]