Microfluidically supported characterization of responses of Rhodococcus erythropolis strains isolated from different soils on Cu-, Ni-, and Co-stress

Abstract

We present a new methodological approach for the assessment of the susceptibility of Rhodococcus erythropolis strains from specific sampling sites in response to increasing heavy metal concentration (Cu2+, Ni2+, and Co2+) using the droplet-based microfluid technique. All isolates belong to the species R. erythropolis identified by Sanger sequencing of the 16S rRNA. The tiny step-wise variation of metal concentrations from zero to the lower mM range in 500 nL droplets not only provided accurate data for critical metal ion concentrations but also resulted in a detailed visualization of the concentration-dependent response of bacterial growth and autofluorescence activity. As a result, some of the isolates showed similar characteristics in heavy metal tolerance against Cu2+, Ni2+, and Co2+. However, significantly different heavy metal tolerances were found for other strains. Surprisingly, samples from the surface soil of ancient copper mining areas supplied mostly strains with a moderate sensitivity to Cu2+, Ni2+, and Co2+, but in contrast, a soil sample from an excavation site of a medieval city that had been covered for about eight centuries showed an extremely high tolerance against cobalt ion (up to 36 mM). The differences among the strains not only may be regarded as results of adaptation to the different environmental conditions faced by the strains in nature but also seem to be related to ancient human activities and temporal partial decoupling of soil elements from the surface. This investigation confirmed that microfluidic screening offers empirical characterization of properties from same species which has been isolated from sites known to have different human activities in the past.

Novel Nanobiocomposites Based on Natural Polysaccharides as Universal Trophic Low-Dose Micronutrients

“…These acids have low reactivity, which makes the surface of mycobacteria waxy and extremely hydrophobic [ 74 ]. According to multiple studies, mycolic acids ensure the resistance of R. erythropolis to various stress factors and pollutants, such as oil products and heavy metals [ 75 , 76 , 77 , 78 , 79 ], and also allow survival on very poor nutrient media [ 80 ]. We assume that the presence of a negative effect of NCs on the viability of Cms is associated with the absence of mycolic acids in the cell wall of this bacterium.…”

Rhodococcus erythropolis ATCC 4277 behavior against different metals and its potential use in waste biomining

“…R. erythropolis is a gram-positive bacterium that is remarkable for its versatile metabolism and applicability in the biodegradation and bioremediation processes due to its heterotrophic capacity to use carbon, alkanes, and others as energy sources [37]. Moreover, R. erythropolis can grow even in extreme pH conditions and metal presence, which is usually associated with metal sites and intrinsic adaptations like sorption mechanisms or fatty acid modulation [38][39][40][41]. This capacity is variable according to metal or metalloid concentrations in the environment.…”

Droplet-based microfluidics as a media optimization tool for cyanobacteria

“…Furthermore, droplet-based microfluidics is in use for detection of antibiotic resistances and for the development of new antibiotics 12 . Besides bacteria, the micro segmented-flow technique has also proven to be suitable for eukaryotic microorganisms such as Chlorella 13 or even embryos of multicellular organisms 14 and for the characterization of the concentrationdependent response of complex unknown environmental bacterial communities on toxic substances 15,16 . As applied to cyanobacterial systems, microfluidics is an emerging technology with only a handful of applications.…”