Bacterium Rhodococcus Sp Research Articles

Carbon metabolism characteristics of quorum quenching bacteria Rhodococcus sp. BH4 determine the bioaugmentation efficiency under different carbon source conditions

Carbon sources are critical factors influencing bacterial bioaugmentation, however, the underlying mechanisms, particularly the metabolic characteristics of bioaugmented bacteria remain poorly understood. The bioaugmented bacterium Rhodococcus sp. BH4 secretes the quorum quenching (QQ) enzyme QsdA to disrupt the quorum sensing (QS) in the activated sludge (AS) process, reducing AS yield in-situ. This study investigated the carbon metabolic characteristics of BH4 and explored the effects on bioaugmentation with different influent carbon sources. Because of the absence of glucose-specific phosphoenol phosphotransferase system (PTS), BH4 prefers sodium acetate to glucose. However, the lactones produced during extracellular glucose metabolism enhance BH4 qsdA expression. Moreover, BH4 possess carbon catabolite repression (CCR), acetate inhibits glucose utilization. BH4 microbeads were added to reactors with different carbon sources (R1: sodium acetate; R2: glucose; R3: a mixture of sodium acetate and glucose) for in-situ AS yield reduction. During operation, AS reduction efficiency decreased in the following order: R1 > R3 > R2. R2 and R3 microbeads exhibited similar QQ activity to R1, with less BH4 biomass at 5 d. 13C labeling and Michaelis-Menten equation showed that, due to differences in the competitiveness of carbon sources, R1 BH4 obtained the most carbon, whereas R2 BH4 obtained the least carbon. Moreover, acetate inhibited glucose utilization of R3 BH4. Transcriptome analysis showed that R1 BH4 qsdA expression was the lowest, R2 BH4 was the most serious form of programmed cell death, and the R3 BH4 PTS pathway was inhibited. At 10 d, R1 BH4 biomass and microbead QQ activity were higher than that in R3, and the R2 BH4 lost viability and QQ activity. This study provides new insights into bioaugmentation from the perspectives of carbon source competitiveness, carbon metabolism pathways, and CCR.

Roles of n-hexadecane in the degradation of dibenzofuran by a biosurfactant-producing bacterium Rhodococcus sp.

The hydrophobic nature of dioxins is a major obstacle to their bioremediation. The present study attempted to improve the bioaccessibility of dioxins in two-phase partitioning bioreactors and activated sludge reactors. Dibenzofuran and n-hexadecane were used as model compounds for dioxins and non-aqueous phase liquids (NAPLs), respectively. First, biosurfactants produced by dioxin-degrading Rhodococcus sp. strain p52 were analyzed. Then, the role of n-hexadecane during the biodegradation of dibenzofuran was evaluated. The results showed that high NAPL ratios (n-hexadecane ≥40 g/L) in the two liquid-phase systems favored dibenzofuran removal, while the cell surface of strain p52 became extremely hydrophobic (>97%), which promoted its adhesion to NAPLs and subsequent transport of dibenzofuran from NAPL to the cells. In addition, a bioaugmented activated sludge reactor with n-hexadecane as the supplemented carbon source could not only facilitate the aerobic granular sludge formation but also improve dibenzofuran removal and the activated sludge settling properties. Simultaneously, conjugative transfer of catabolic plasmids was promoted. This study demonstrated the potential application of strain p52 with NAPLs for the bioremediation of dioxins.

Enhancing the sewage treatment effect, reducing membrane fouling, and increasing microbial community diversity by a novel biofiller-carrying functional bacteria Rhodococcus sp. CPZ24 in a moving bed biofilm reactor

The feasibility of using a novel moving bed biofilm reactor (fbMBBR) with biofiller-carrying functional bacteria, Rhodococcus sp. CPZ24, to alleviate membrane pollution and improve wastewater treatment was studied. Three membrane reactors, namely, a biofilm reactor (MBR), a convention moving bed biofilm reactor (MBBR), and fbMBBR, were compared. The results showed that the efficiency of sewage treatment by the fbMBBR was significantly better than that of the MBR and MBBR. When the HRT and DO were 6 h and 3 mg·L−1, the removal rates of NH4+-N, COD, TN, and TP in the fbMBBR reached 92.76 %, 89.89 %, 82.24 %, and 68.23 %, respectively, and membrane fouling was effectively alleviated. Furthermore, the novel biofiller improved the abundance of dominant microbial community species on the membrane module and strengthened microbial community functions. In summary, this study presented a novel fbMBBR with excellent performance in sewage treatment, reducing membrane pollution.

Whole-cell studies of substrate and inhibitor specificity of isoprene monooxygenase and related enzymes.

Co-oxidation of a range of alkenes, dienes, and aromatic compounds by whole cells of the isoprene-degrading bacterium Rhodococcus sp. AD45 expressing isoprene monooxygenase was investigated, revealing a relatively broad substrate specificity for this soluble diiron centre monooxygenase. A range of 1-alkynes (C2 -C8 ) were tested as potential inhibitors. Acetylene, a potent inhibitor of the related enzyme soluble methane monooxygenase, had little inhibitory effect, whereas 1-octyne was a potent inhibitor of isoprene monooxygenase, indicating that 1-octyne could potentially be used as a specific inhibitor to differentiate between isoprene consumption by bona fide isoprene degraders and co-oxidation of isoprene by other oxygenase-containing bacteria, such as methanotrophs, in environmental samples. The isoprene oxidation kinetics of a variety of monooxygenase-expressing bacteria were also investigated, revealing that alkene monooxygenase from Xanthobacter and soluble methane monooxygenases from Methylococcus and Methylocella, but not particulate methane monooxygenases from Methylococcus or Methylomicrobium, could co-oxidise isoprene at appreciable rates. Interestingly the ammonia monooxygenase from the nitrifier Nitrosomonas europaea could also co-oxidise isoprene at relatively high rates, suggesting that co-oxidation of isoprene by additional groups of bacteria, under the right conditions, might occur in the environment.

Degradation of low-density polyethylene by the bacterium Rhodococcus sp. C-2 isolated from seawater

Low-density polyethylene (LDPE), which accounts for 20% of the global plastic production, is discharged in great quantities into the ocean, threatening marine life and ecosystems. Marine microorganisms have previously been reported to degrade LDPE plastics; however, the exploration of strains and enzymes that degrade LDPE is still limited. Here, an LDPE-degrading bacterium was isolated from seawater of the Changjiang Estuary, China and identified as Rhodococcus sp. C-2, the relative abundance of which was dramatically enhanced during PE-degrading microbial enrichment. The strain C-2 exhibited the degradation of LDPE films, leading to their morphological deterioration, reduced hydrophobicity and tensile strength, weight loss, as well as the formation of oxygen-containing functional groups in short-chain products. Sixteen bacterial enzymes potentially involved in LDPE degradation were screened using genomic, transcriptomic, and degradation product analyses. Thereinto, the glutathione peroxidase GPx with exposed active sites catalyzed the LDPE depolymerization with the cooperation of its dissociated superoxide anion radicals. Furthermore, an LDPE degradation model involving multiple enzymes was proposed. The present study identifies a novel PE-degrading enzyme (PEase) for polyethylene bioremediation and promotes the understanding of LDPE degradation.

Changes in membrane fatty acids of a halo-psychrophile exposed to magnesium perchlorate and low temperatures: Implications for Mars habitability

The presence of perchlorate salts in aqueous solutions bears two opposite effects on habitability. On the one hand, perchlorate salts trigger a decrease in the freezing point of the aqueous solutions, resulting in stable aqueous solutions at subzero temperatures, thereby widening the habitable conditions for potential microbial life. On the other hand, the presence of perchlorates in solution imposes a significant osmotic stress that compromises the integrity of microbial cell membranes, thereby restricting the habitable conditions in the same aqueous environment. Here we investigated the survivability and the changes in the composition of membrane fatty acids (FAs) of the bacterium Rhodococcus sp. JG-3 cells under warm (20°C), cold (4°C), and subzero temperatures (−10°C and −16°C), and in the presence (8 wt% and 16 wt%) and absence of magnesium perchlorate (Mg(ClO4)2). Bacterial cell survivability decreased with decreasing temperature and presence of magnesium perchlorate. However, Rhodococcus sp. JG-3 was able to tolerate up to 8 wt% Mg(ClO4)2 at −16°C. The presence of magnesium perchlorate in the medium decreased the concentration of total FAs, likely due to a destabilization of the molecules by the chaotropic effect of the perchlorate anion. At the maximum stress (both subzero temperatures and 16 wt% magnesium perchlorate), the composition of FAs changed, i.e., Rhodococcus sp. JG-3 cells increased the relative abundance of saturated FAs (SFAs) over the unsaturated (UFAs) or branched (BFAs). These changes in the proportion of FAs types may be a physiological response during cooling, aimed to improve lipid membrane stability. Interestingly, the composition and relative abundance of fatty acid types (i.e., SFAs, UFAs and BFAs) of Rhodococcus sp. JG-3 when simultaneously exposed to subzero temperatures and 16 wt% magnesium perchlorate was similar to that following freezing stress alone, suggesting that either both conditions triggered a similar response or that one response dominated over the other. Our findings contribute to understand the survivability and adaptation of extremophilic microorganisms under polyextreme conditions, such as those existing in the Martian subsurface today and/or in the past, which include the documented presence of magnesium perchlorate salts in ancient sediments and global cold temperatures.

Prolonging the Life Span of Membrane in Submerged MBR by the Application of Different Anti-Biofouling Techniques.

The membrane bioreactor (MBR) is an efficient technology for the treatment of municipal and industrial wastewater for the last two decades. It is a single stage process with smaller footprints and a higher removal efficiency of organic compounds compared with the conventional activated sludge process. However, the major drawback of the MBR is membrane biofouling which decreases the life span of the membrane and automatically increases the operational cost. This review is exploring different anti-biofouling techniques of the state-of-the-art, i.e., quorum quenching (QQ) and model-based approaches. The former is a relatively recent strategy used to mitigate biofouling. It disrupts the cell-to-cell communication of bacteria responsible for biofouling in the sludge. For example, the two strains of bacteria Rhodococcus sp. BH4 and Pseudomonas putida are very effective in the disruption of quorum sensing (QS). Thus, they are recognized as useful QQ bacteria. Furthermore, the model-based anti-fouling strategies are also very promising in preventing biofouling at very early stages of initialization. Nevertheless, biofouling is an extremely complex phenomenon and the influence of various parameters whether physical or biological on its development is not completely understood. Advancing digital technologies, combined with novel Big Data analytics and optimization techniques offer great opportunities for creating intelligent systems that can effectively address the challenges of MBR biofouling.

Isolation and Characterization of 1-Hydroxy-2,6,6-trimethyl-4-oxo-2-cyclohexene-1-acetic Acid, a Metabolite in Bacterial Transformation of Abscisic Acid.

We report the discovery of a new abscisic acid (ABA) metabolite, found in the course of a mass spectrometric study of ABA metabolism by the rhizosphere bacterium Rhodococcus sp. P1Y. Analogue of (+)-ABA, enriched in tritium in the cyclohexene moiety, was fed in bacterial cells, and extracts containing radioactive metabolites were purified and analyzed to determine their structure. We obtained mass spectral fragmentation patterns and nuclear magnetic resonance spectra of a new metabolite of ABA identified as 1-hydroxy-2,6,6-trimethyl-4-oxo-2-cyclohexene-1-acetic acid, which we named rhodococcal acid (RA) and characterized using several other techniques. This metabolite is the second bacterial ABA degradation product in addition to dehydrovomifoliol that we described earlier. Taken together, these data reveal an unknown ABA catabolic pathway that begins with side chain disassembly, as opposed to the conversion of the cyclohexene moiety in plants. The role of ABA-utilizing bacteria in interactions with other microorganisms and plants is also discussed.

Structural characterization of phosphinothricin N -acetyltransferase ( RePAT ) and the glufosinate-resistant analysis for site-directed mutagenesis of RePAT in Arabidopsis thaliana

Background Transferring herbicide resistance genes to plant cultivars is one of the most effective methods for managing weed growth in agricultural land. The RePAT gene, previously isolated from the marine bacterium Rhodococcus sp . strain YM12, was found to provide glufosinate resistance to plants. Objective In this study, we further investigated the protein structure and function of RePAT isolated from the marine. Methods The physicochemical properties, two-dimensional structure, three-dimensional structure, and functional domains of the RePAT protein were analyzed [...]

Biodegradation of di-(2-ethylhexyl) phthalate by novel Rhodococcus sp. PFS1 strain isolated from paddy field soil.

Di-(2-ethylhexyl)-phthalate (DEHP) is the phthalate ester frequently utilized as a plasticizer, commonly found in cosmetics, packaging materials; moreover, it has carcinogenic and mutagenic effects on humans. In the current study, we isolated the soil bacterium Rhodococcus sp. PFS1 and to assess its DEHP degradation ability in various environmental conditions. The strain PFS1 was isolated from paddy field soil and identified by the 16S rRNA sequencing analyses. The strain PFS1 was examined for its biodegradation ability of DEHP at various pH, temperature, salt concentration, glucose concentration, and high and low concentrations of DEHP. Moreover, the biodegradation of DEHP at a contaminated soil environment by strain PFS1 was assessed. Further, the metabolic pathway of DEHP degradation by PFS1 was analyzed by HPLC-MS analysis. The results showed that the strain PFS1 effectively degraded the DEHP at neutral pH and temperature 30°C; moreover, expressed excellent DEHP degradation at the high salt concentration (up to 50g/L). The strain PFS1 was efficiently degraded the different tested phthalate esters (PAEs) up to 90%, significantly removed the DEHP contamination in soil along with native organisms which are present in soil up to 94.66%; nevertheless, the PFS1 alone degraded the DEHP up to 87.665% in sterilized soil. According to HPLC-MS analysis, DEHP was degraded into phthalate (PA) by PFS1 strain via mono(2-ethylehxyl) phthalate (MEHP); then PA was utilized for cell growth. These results suggest that Rhodococcus sp. PFS1 has excellent potential to degrade DEHP at various environmental conditions especially in contaminated paddy field soil.

DNA photolyase from Antarctic marine bacterium Rhodococcus sp. NJ-530 can repair DNA damage caused by ultraviolet.

The online version contains supplementary material available at 10.1007/s13205-021-02660-8.

Конструирование и функциональный анализ рекомбинантных штаммов Mycolicibacterium smegmatis, несущих гены бациллярных цитохромов CYP106A1 и CYP106A2

Mycolicibacterium smegmatis mc2155 has been genetically modified to be used as a platform for the expression of foreign cytochrome P450 monooxygenases by introducing deletions in the kshB and kstD genes that encode key stages of the enzymatic destruction of the steroid nucleus. Three sets of genetic constructs have been created for heterologous expression of the genes of cytochromes P450 CYP106A1 from Bacillus megaterium DSM319 and CYP106A2 from Bacillus megaterium ATCC13368 in Mycolicibacterium smegmatis mc2155 (ΔkshBΔkstD) cells. The recombinant plasmids contained monocistronic expression cassettes of cytochrome genes (NS31 and pNS32), or tricistronic cassettes of cytochrome genes together with cDNA copies of adrenodoxin and andrenodoxin reductase genes of the bovine adrenal cortex (pNS33 and pNS34), or monocistronic gene cassettes of chimeric cytochromes fused with the DNA sequence encoding the CYP116B2 reductase domain from the soil bacterium Rhodococcus sp. NCIMB 9784 (pNS35 and pNS36). The recombinant strains of mycolicibacteria were shown to selectively monohydroxylate androstenedione (AD) under growth conditions. The product was identified as 15-hydroxyandrostenedione (15-OH-AD) by mass spectrometry and 1H and 13C NMR spectroscopy. The maximum level of 15-OH-AD production (17.3 ± 1.5 mg/L) was observed when using the recombinant M. smegmatis mc2155 (ΔkshBΔkstD) (pNS32) strain, which expresses a single cyp106A2 gene from B. megaterium ATCC13368. Host proteins of M. smegmatis mc2155 were shown to be capable of supplying electrons to heterologous cytochromes to support their hydroxylating activity. The results are of priority character, expand the understanding of the hydroxylation of steroid compounds by bacterial cytochromes CYP106A1/A2 and are important for the creation of microbial strains producing valuable hydroxysteroids. cyp106A1, cyp106A2, cytochrome P450, heterologous expression, Bacillus megaterium, Mycolicibacterium smegmatis, 15β-hydroxylation, bioconversion, steroids This work was supported by the Russian Science Foundation (project No. 21-64-00024).

Chemical and biological investigation of the marine bacterium Rhodococcus sp. UA13

In this work, a new indole alkaloid, rhodindohyde was isolated from the ethyl acetate fraction of the marine bacterium Rhodococcus sp. UA13, previously obtained from the Red Sea sponge Callyspongia aff. implexa. The structure of the new compound was identified with the aid of 1D and 2D NMR experiments, as well as HR-ESI-MS technique. Rhodindohyde was found to exert weak inhibitory activities (IC50 > 100 μg/mL) against both Staphylococcus aureus NCTC 8325 and Trypanosoma brucei brucei TC221. On the other hand, a limited number of studies have deliberated the anti-inflammatory and pain-relieving potential of marine bacteria and their natural metabolites as yet; therefore, the possible analgesic, anti-inflammatory, and antipyretic properties of the methanol fraction of Rhodococcus sp. UA13 were explored using a number of pharmacologically relevant test models. Results showed that the methanol fraction have demonstrated noticeable and statistically significant activities that were also comparable to those of the tested reference drugs; highlighting the helpful role of marine actinomycetes in developing of future therapeutic agents against inflammatory conditions associated with pains and fever.

Can Halophilic and Psychrophilic Microorganisms Modify the Freezing/Melting Curve of Cold Salty Solutions? Implications for Mars Habitability.

We present the hypothesis that microorganisms can change the freezing/melting curve of cold salty solutions by protein expression, as it is known that proteins can affect the liquid-to-ice transition, an ability that could be of ecological advantage for organisms on Earth and on Mars. We tested our hypothesis by identifying a suitable candidate, the well-known psycrophile and halotolerant bacteria Rhodococcus sp. JG3, and analyzing its response in culture conditions that included specific hygroscopic salts relevant to Mars—that is, highly concentrated magnesium perchlorate solutions of 20 wt % and 50 wt % Mg(ClO4)2 at both end members of the eutectic concentration (44 wt %)—and subfreezing temperatures (263 K and 253 K). Using a combination of techniques of molecular microbiology and aqueous geochemistry, we evaluated the potential roles of proteins over- or underexpressed as important players in different mechanisms for the adaptability of life to cold environments. We recorded the changes observed by micro-differential scanning calorimetry. Unfortunately, Rhodococcus sp. JG3 did not show our hypothesized effect on the melting characteristics of cold Mg-perchlorate solutions. However, the question remains as to whether our novel hypothesis that halophilic/psychrophilic bacteria or archaea can alter the freezing/melting curve of salt solutions could be validated. The null result obtained after analyzing just one case lays the foundation to continue the search for proteins produced by microorganisms that thrive in very cold, high-saline solutions, which would involve testing different microorganisms with different salt components. The immediate implications for the habitability of Mars are discussed.

Characterization of a novel carbendazim-degrading strain Rhodococcus sp. CX-1 revealed by genome and transcriptome analyses

The persistence and ecotoxicity of carbendazim residues pose a potential risk to environmental ecology and human health. Here, a novel and highly efficient carbendazim-degrading bacterium Rhodococcus sp. CX-1, capable of utilizing carbendazim as its sole source of carbon and energy, was isolated from contaminated soil. The biodegradation characteristics and metabolic pathways were studied by mass spectrometry, genomic annotation, and transcriptome analysis. The degradation rate of carbendazim by strain CX-1 was 3.98–9.90 mg/L/h under different conditions, and the optimum degradation conditions were 40 °C and pH 7.0. The addition of carbon sources (glucose, fructose, and sucrose, 100 mg/L) could accelerate carbendazim degradation. HPLC-MS/MS identification suggested that carbendazim is first hydrolyzed into 2-aminobenzimidazole and then to 2-hydroxybenzimidazole, and is ultimately mineralized to carbon dioxide. The genome of strain CX-1 contained 6,511,628 bp nucleotides, 2 linear plasmids, 2 circular plasmids, and 6437 protein coding genes. Genome annotation and transcriptome analysis indicated that carbendazim degradation may be regulated by the degradation genes harbored in the chromosome and in plasmid 2, and two different degradation pathways of carbendazim by imidazole ring cleavage or benzene ring cleavage were predicted. This study provided new insight to reveal the biodegradation mechanism of carbendazim; furthermore, strain CX-1 is a promising bioresource for carbendazim bioremediation.

Biodegradation of Phenol by Rhodococcus sp. Strain SKC: Characterization and Kinetics Study.

This study focuses on the kinetics of a pure strain of bacterium Rhodococcus sp. SKC, isolated from phenol-contaminated soil, for the biodegradation of phenol as its sole carbon and energy source in aqueous medium. The kinetics of phenol biodegradation including the lag phase, the maximum phenol degradation rate, maximum growth rate (Rm) and maximum yield coefficient (Y) for each Si (initial phenol concentration, mg/L) were fitted using the Gompertz and Haldane models of substrate inhibition (R2 > 0.9904, RMSE < 0.00925). The values of these parameters at optimum conditions were μmax = 0.30 h−1, Ks = 36.40 mg/L, and Ki = 418.79 mg/L, and that means the inhibition concentration of phenol was 418.79 mg/L. By comparing with other strains of bacteria, Rhodococcus sp. SKC exhibited a high yield factor and tolerance towards phenol. This study demonstrates the potential application of Rhodococcus sp. SKC for the bioremediation of phenol contaminate.

Isoprene Oxidation by the Gram-Negative Model bacterium Variovorax sp. WS11.

Plant-produced isoprene (2-methyl-1,3-butadiene) represents a significant portion of global volatile organic compound production, equaled only by methane. A metabolic pathway for the degradation of isoprene was first described for the Gram-positive bacterium Rhodococcus sp. AD45, and an alternative model organism has yet to be characterised. Here, we report the characterisation of a novel Gram-negative isoprene-degrading bacterium, Variovorax sp. WS11. Isoprene metabolism in this bacterium involves a plasmid-encoded iso metabolic gene cluster which differs from that found in Rhodococcus sp. AD45 in terms of organisation and regulation. Expression of iso metabolic genes is significantly upregulated by both isoprene and epoxyisoprene. The enzyme responsible for the initial oxidation of isoprene, isoprene monooxygenase, oxidises a wide range of alkene substrates in a manner which is strongly influenced by the presence of alkyl side-chains and differs from other well-characterised soluble diiron monooxygenases according to its response to alkyne inhibitors. This study presents Variovorax sp. WS11 as both a comparative and contrasting model organism for the study of isoprene metabolism in bacteria, aiding our understanding of the conservation of this biochemical pathway across diverse ecological niches.

Genes and novel sRNAs involved in PAHs degradation in marine bacteria Rhodococcus sp. P14 revealed by the genome and transcriptome analysis.

Rhodococcus sp. P14 is able to degrade various polycyclic aromatic hydrocarbons (PAHs). In this study, 6 ring-hydroxylating dioxygenases and 24 monooxygenases genes related to PAHs degradation were identified in its genome. Moreover, various genes, like serine hydrolase, hydratase, alcohol dehydrogenase, protocatechuate 3,4-dioxygenase, β-ketoadipate CoA transferase and β-Ketoadipyl CoA thiolase, which were supposed to be involved in PAHs degradation were also identified. Based on the genome analysis, the proposed PAHs degradation pathway was constructed in P14 strain, which showed that PAHs was degraded into the acetyl CoA and succinyl CoA, then mineralized to CO2 via the TCA cycle. Furthermore, several genes, including cytochrome P450 (RS16725; RS16695; RS12220), catalase (RS15825), dehydrogenase (RS15755; RS18420) and hydrolase (RS16460; RS24665), showed increased expression level during PAHs degradation according to the transcriptome data. In addition, 12 novel sRNAs which were supposed to have the regulation function in PAHs degradation were identified. This study gives us the outlook of PAHs degradation pathway in Rhodococcus sp. P14. Moreover, it first demonstrates that sRNAs may harbor the regulation function in PAHs degradation.

Discrepant roles of a quorum quenching bacterium (Rhodococcus sp. BH4) in growing dual-species biofilms

Quorum quenching (QQ) is a promising alternative method for biofilm control. However, a largely unexplored issue is the mechanism through which QQ bacteria interact with biofilm-forming bacteria. Here, we explore inter-species interactions during biofilm development (using 96-well polystyrene plates in a static incubator) between the QQ bacterium Rhodococcus sp. BH4 and sludge bacteria. Experimental results revealed that strain BH4 provoked both competitive (76%) and cooperative (24%) interactions (P < 0.05) in dual-species biofilms after 24 h of incubation (mature biofilm), implying that signal destruction by strain BH4 was strain-dependent. Besides hike in the biofilm biomass (~21%), amount of extracellular polymeric substances (EPS) (25–30 times) and particle size (3.5 times) in the Serratia sp. JSB1 biofilm were increased by str. BH4. This suggests that strain BH4 may only have quenching effects against certain bacteria, and that such effects are overlooked at the community level. Taken together, present results imply that in a given biofilm community, not all QS-bacteria interact similarly with Rhodococcus sp. BH4, either because QS-bacteria are tolerant of strain BH4 or QS-bacteria have more than one mechanism for biofilm development. Overall, the QQ-strategy alone seems ineffective at controlling biofilm development, although it may be used in combination with other strategies.

INTERAÇÕES COMPETITIVAS DE COMPLEXOS DE RUTÊNIO CONTENDO DIMETILSULFÓXIDO E LIGANTES N-HETEROCÍCLICOS COM ALBUMINA DE SORO HUMANO

Nowadays the discovery of new compounds from microorganisms has substantially decreased. Genomic studies have shown that certain genes are not expressed under standard laboratory conditions. In order to overcome this problem, several methods including microorganism co-culture have been developed. The aim of this work was to select binary co-cultures of marine-derived microorganisms to pursue further chemical studies. From 15 microorganisms, 151 interactions assays in solid media were performed using two different methodologies: distance assays and contact assays that allowed to distinguish between interactions due to diffusible compounds or due to cell-cell contact. For distance assays, the metabolic production changes were evaluated using 3 zones: two corresponding to each microorganism colony, and a third zone corresponding to the interaction zone. This division zone strategy allowed to assess the diffusion compounds gradient, and to suggest the producer microorganism of the induced compounds. The metabolic production of the co-cultures was evaluated using HPLC-DAD and NMR. Seven co-cultures were identified to be able to induce changes in the metabolic production. Remarkably, the co-culture between the fungus Purpureocillium sp. PNM-67 and the bacteria Rhodococcus sp. RKHC-26 or Gordonia sp. PNM-25 induce production of a red dye in the fungus. These are the first successful examples of interaction between a fungus and a mycolic acid-containing bacteria.