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Interaction of Rhodococcus with Metals and Biotechnological Applications
No full textIn studies of environmental stresses caused by metals, Rhodococcus species are routinely identified as part of a beneficial microbial rhizosphere community. These bacterial strains, inhabiting diverse ecological niches, possess a variety of enzymatic activities to carry out relevant biodegradation reactions, such as degradation of organic pollutants in some cases using them for both carbon and energy. In this context, most Rhodococcus strains have been found to have very high levels of metal resistance. Thus, these microorganisms are not only capable of metabolizing various organic pollutants in the presence of co-contaminating heavy metals, but they can also bioadsorb and/or bioconvert various metals and metalloids [metal(loid)s]. Indeed, some Rhodococcus exploit these metal(loid) compounds to generate biogenic nanoscale materials of intriguing physical-chemical properties, which can find applications in biotechnology.
This book chapter has the focus in overviewing the biotechnological relevance of the Rhodococcus genus relationship with metal(loid)s, the bioprocesses elicited by these microorganisms in handling metal(loid)s’ toxicity, and the importance of these actinomycetes in the context of the bioremediation and bionanotechnology fields
From 0D-complex to 3D-MOF: changing the antimicrobial activity of zinc(II) via reaction with aminocinnamic acids
Full text linkCombining zinc nitrate with 3- and/or 4- aminocinnamic acid (3-ACA and 4-ACA, respectively) leads to the formation of the 0D complex [Zn(4-AC)2(H2O)2], the 1D coordination polymer [Zn(3-AC)(4-AC)], and the 2D and 3D MOFs [Zn(3-AC)2]∙2H2O and [Zn(4-AC)2]∙H2O, respectively. These compounds result from the deprotonation of the acid molecules, with the resulting 3- and 4-aminocinnamate anions serving as bidentate terminal or bridging ligands. All solids were fully characterized via single crystal and powder X-ray diffraction and thermal techniques. Given the mild antimicrobial properties of cinnamic acid derivatives and the antibacterial nature of the metal cation, these compounds were assessed and demonstrated very good planktonic cell killing as well as inhibition of biofilm growth against Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus
Tunable photoluminescence properties of selenium nanoparticles: biogenic versus chemogenic synthesis
Full text linkVarious technological and biomedical applications
rely on the ability of materials to emit light (photoluminescence
[PL]), and, among them, metal nanoparticles
(NPs) and semi-conductor Quantum Dots (QDs) represent
ideal candidates as sensing probes and imaging tools, portraying
better PL features than conventional organic dyes.
However,theknowledgeofPLbehaviorofsemiconductorNPs
– i.e., selenium; SeNPs – is still in its infancy, especially for
those synthesized by microorganisms. Considering the
essential role played by biogenic SeNPs as antimicrobial,
anticancer, and antioxidant agents, or food supplements,
their PL properties must be explored to take full advantage of
them as eco-friendly and versatile tools. Here, PL features of
SeNPs produced by the Se-tolerant Stenotrophomonasmaltophilia
SeITE02 strain, compared with chemogenic ones, are
investigated, highlighting the PL dependency on the NP size.
Indeed, PL emission shifted from indigo-blue (emission
wavelength λem 400–450 nm) to green-yellow (λem 480–
570 nm) and orange-red (λem 580–700 nm) for small (ca.
50 nm) and big (ca. 100 nm) SeNPs respectively, revealing the
versatility of an environmental bacterial isolate to synthesize
diverse PL probes. Besides, biogenic SeNPs show PL lifetime
comparable to those of the most used fluorophores, supporting
their potential application as markers for (bio)imaging
A comparison of the response of two Burkholderia fungorum strains grown as planktonic cells versus biofilm to dibenzothiophene and select polycyclic aromatic hydrocarbons
Full text linkIn natural environments, bacteria often exist in close association with surfaces and interfaces by establishing biofilms. Here, we report on the ability of Burkholderia fungorum strains DBT1 and 95 to survive in high concentrations of hydrocarbons, and we compare their growth as a biofilm vs. planktonic cells. The 2 compounds tested were dibenzothiophene (DBT) and a mixture of naphthalene, phenanthrene, and pyrene (5:2:1) as representative compounds of thiophenes and polycyclic aromatic hydrocarbons (PAHs), respectively. The results showed that both strains were able to degrade DBT and to survive in the presence of up to a 2000 mg·L−1 concentration of this compound both as a biofilm and as free-living cells. Moreover, B. fungorum DBT1 showed reduced tolerance towards the mixed PAHs (2000 mg·L−1 naphthalene, 800 mg·L−1 phenanthrene, and 400 mg·L−1 pyrene) both as a biofilm and as free-living cells. Conversely, biofilms of B. fungorum 95 enhanced resistance against these toxic compounds compared with planktonic cells (P < 0.05). Visual observation through confocal laser scanning microscopy showed that exposure of biofilms to DBT and PAHs altered their structure: high concentrations of DBT triggered an aggregation of biofilm cells. These findings provide new perspectives on the effectiveness of using DBT-degrading bacterial strains in bioremediation of hydrocarbon-contaminated sites
The Role of cheA Genes in Swarming and Swimming Motility of Pseudomonas pseudoalcaligenes KF707
Full text linkA genome analysis of Pseudomonas pseudoalcaligenes KF707, a PCBs degrader and metal-resistant soil microorganism, revealed the presence of two novel gene clusters named che2 and che3, which were predicted to be involved in chemotaxis-like pathways, in addition to a che1 gene cluster. We herein report that the histidine kinase coding genes, cheA2 and cheA3, have no role in swimming or chemotaxis in P. pseudoalcaligenes KF707, in contrast to cheA1. However, the cheA1 and cheA2 genes were both necessary for cell swarming, whereas the cheA3 gene product had a negative effect on the optimal swarming phenotype of KF707 cells
Biphenyl Modulates the Expression and Function of Respiratory Oxidases in the Polychlorinated-Biphenyls Degrader Pseudomonas pseudoalcaligenes KF707
Full text linkPseudomonas pseudoalcaligenes KF707 is a soil bacterium which is known for its capacity to aerobically degrade harmful organic compounds such as polychlorinated biphenyls (PCBs) using biphenyl as co-metabolite. Here we provide the first genetic and functional analysis of the KF707 respiratory terminal oxidases in cells grown with two different carbon sources: glucose and biphenyl. We identified five terminal oxidases in KF707: two c(c)aa3 type oxidases (Caa3 and Ccaa3), two cbb3 type oxidases (Cbb31 and Cbb32), and one bd type cyanide-insensitive quinol oxidase (CIO). While the activity and expression of both Cbb31 and Cbb32 oxidases was prevalent in glucose grown cells as compared to the other oxidases, the activity and expression of the Caa3 oxidase increased considerably only when biphenyl was used as carbon source in contrast to the Cbb32 oxidase which was repressed. Further, the respiratory activity and expression of CIO was up-regulated in a Cbb31 deletion strain as compared to W.T. whereas the CIO up-regulation was not present in Cbb32 and C(c)aa3 deletion mutants. These results, together, reveal that both function and expression of cbb3 and caa3 type oxidases in KF707 are modulated by biphenyl which is the co-metabolite needed for the activation of the PCBs-degradation pathway
Editorial: Metal organic frameworks for antimicrobial prevention and treatments
Full text linkWe have entered what is now referred to as the antimicrobial resistance (AMR) era,
where resistance to existing antibiotics and antiseptics by bacteria has become increasing the
norm. Unfortunately, the development of new antibiotics has declined as the rates of
resistance increased. The WHO and the UN has defined this as the hidden pandemic and
the greatest threat to human health and food security. To address this problem alternative
approaches to traditional antibiotics are being explored that include but not limited to,
antimicrobial peptides, bacteriophage, resistance inhibitors, vaccines, probiotics, natural
plant compounds, CRISPR vectors etc. One approach has been to revisit metal elements,
which were used as antimicrobials since antiquity and forgotten about with the discovery of
antibiotics. Metal elements provide multifactorial killing on microbes (Lemire et al., 2013).
The mode of delivery of metallo-antimicrobials may be as the metal salt, an alloy,
organometallics, complexes, nanomaterial and of increasing interest, metal-organic
frameworks (MOFs) (Turner, 2023)
Biotechnology of Rhodococcus for the production of valuable compounds
Full text linkBacteria belonging to Rhodococcus genus represent ideal candidates for microbial biotechnology applications because of their
metabolic versatility, ability to degrade a wide range of organic compounds, and resistance to various stress conditions, such as
metal toxicity, desiccation, and high concentration of organic solvents. Rhodococcus spp. strains have also peculiar biosynthetic
activities that contribute to their strong persistence in harsh and contaminated environments and provide them a competitive
advantage over other microorganisms. This review is focused on the metabolic features of Rhodococcus genus and their potential
use in biotechnology strategies for the production of compounds with environmental, industrial, and medical relevance such as
biosurfactants, bioflocculants, carotenoids, triacylglycerols, polyhydroxyalkanoate, siderophores, antimicrobials, and metalbased
nanostructures. These biosynthetic capacities can also be exploited to obtain high value-added products from low-cost
substrates (industrial wastes and contaminants), offering the possibility to efficiently recover valuable resources and providing
possible waste disposal solutions. Rhodococcus spp. strains have also recently been pointed out as a source of novel bioactive
molecules highlighting the need to extend the knowledge on biosynthetic capacities of members of this genus and their potential
utilization in the framework of bioeconomy
Antimicrobial activity of supramolecular salts of gallium(III) and proflavine and the intriguing case of a trioxalate complex
Full text linkThe use of the gallium oxalate complex [Ga(ox)(3)](3-) as a building block in the formation of a drug-drug salt with the antimicrobial agent proflavine (PF) as its proflavinium cation (HPF+), namely [HPF](3)[Ga(ox)(3)]center dot 4H(2)O, is reported together with the preparation of the potassium salt K-3[Ga(ox)(3)] and the novel dimeric gallium(III) salt K-4[Ga-2(ox)(4)(mu-OH)(2)]center dot 2H(2)O. All compounds have been characterized by solid state methods, and their performance as antimicrobial agents has been evaluated by disk diffusion assay against the bacteria strains Pseudomonas aeruginosa ATCC27853, Staphylococcus aureus ATCC25923, and Escherichia coli ATCC25922. While the [HPF](3)[Ga(ox)(3)]center dot 4H(2)O drug-drug salt is effective against all three strains, the gallium oxalate salt K-3[Ga(ox)(3)] showed impressive selectivity towards P. aeruginosa, with little to no antimicrobial activity against the other two organisms. This work presents novel breakthroughs towards Ga based antimicrobial agents
On the role of a specific insert in acetate permeases (ActP) for tellurite uptake in bacteria: Functional and structural studies
No full textThe oxyanion tellurite (TeO32-) is extremely toxic to bacterial cells. In Rhodobacter capsulatus, tellurite enters the cytosol by means of the high uptake-rate acetate permease RcActP2, encoded by one of the three actP genes present in this species (actP1, actP2 and actP3). Conversely, in Escherichia coli a low rate influx of the oxyanion is measured, which depends mainly on the phosphate transporter EcPitA, even though E. coli contains its own EcActP acetate permease. Here we report that when the actP2 gene from R. capsulatus is expressed in wild-type E. coli HB101 and in E. coli JW3460 δpitA mutant, the cellular intake of tellurite increases up to four times, suggesting intrinsic structural differences between EcActP and RcActP2. Indeed, a sequence analysis indicated the presence in RcActP2 of an insert of 15-16 residues, located between trans-membrane (TM) helices 6 and 7, which is absent in both EcActP and RcActP1. Based on this observation, the molecular models of homodimeric RcActP1 and RcActP2 were calculated and analyzed. In the RcActP2 model, the insert induces a perturbation in the conformation of the loop between TM helices 6 and 7, located at the RcActP2 dimerization interface. This perturbation opens a cavity on the periplasmic side that is closed, instead, in the RcActP1 model. This cavity also features an increase of the positive electric potential on the protein surface, an effect ascribed to specific residues Lys261, Lys281 and Arg560. We propose that this positively charged patch in RcActP2 is involved in recognition and translocation of the TeO32- anion, attributing to RcActP2 a greater ability as compared to RcActP1 to transport this inorganic poison inside the cells
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