Acinetobacter Sp Research Articles

Freezing and thawing in Antarctica: characterization of antifreeze protein (AFP) producing microorganisms isolated from King George Island, Antarctica.

Antarctic temperature variations and long periods of freezing shaped the evolution of microorganisms with unique survival mechanisms. These resilient organisms exhibit several adaptations for life in extreme cold. In such ecosystems, microorganisms endure the absence of liquid water and exhibit resistance to freezing by producing water-binding molecules such as antifreeze proteins (AFP). AFPs modify the ice structure, lower the freezing point, and inhibit recrystallization. The objective of this study was to select and identify microorganisms isolated from different Antarctic ecosystems based on their resistance to temperatures below 0°C. Furthermore, the study sought to characterize these microorganisms regarding their potential antifreeze adaptive mechanisms. Samples of soil, moss, permafrost, and marine sediment were collected on King George Island, located in the South Shetland archipelago, Antarctica. Bacteria and yeasts were isolated and subjected to freezing-resistance and ice recrystallization inhibition (IR) tests. A total of 215 microorganisms were isolated, out of which 118 were molecularly identified through molecular analysis using the 16S rRNA and ITS regions. Furthermore, our study identified 24 freezing-resistant isolates, including two yeasts and 22 bacteria. A total of 131 protein extracts were subjected to the IR test, revealing 14 isolates positive for AFP production. Finally, four isolates showed both freeze-resistance and IR activity (Arthrobacter sp. BGS04, Pseudomonas sp. BGS05, Cryobacterium sp. P64, and Acinetobacter sp. M1_25C). This study emphasizes the diversity of Antarctic microorganisms with the ability to tolerate freezing conditions. These microorganisms warrant further investigation to conduct a comprehensive analysis of their antifreeze capabilities, with the goal of exploring their potential for future biotechnological applications.

Nutrients, surfactants, and aeration in constructed wetlands affect bacterial persistence and metabolic activity during the remediation of crude oil-contaminated water

The use of constructed wetlands (CWs) is one of the best options to treat wastewater. In CWs, microorganisms play a major role in the degradation of organic pollutants but the concentration of nutrients, surfactant, and aeration (NSA) in oil-contaminated water is one of the factors that affect the persistence and metabolic functioning of hydrocarbon-degrading microorganisms. In the present investigation, the influence of the addition of NSA on the persistence of the augmented bacteria, copy of (alkane hydroxylase gene) alkB gene, and its expression level in the water, soil, and plants of CWs were evaluated. The CWs mesocosms were developed by the vegetation of Typha latifolia and Cyperus laevigatus and inoculated with the bacterial consortium (Pseudomonas putida TYRI39, Acinetobacter junii TYRH47, Acinetobacter sp. CYRH17, Pseudomonas sp. CYSI27, and Pseudomonas sp. TYRH42). The mesocosms were provided with nutrients (20 mg l− 1 N, 2.6 mg l− 1 P, and 16.4 mg l− 1 K) in liquid form, surfactant Tween-20 (0.2%, v/v) in liquid form, and aeration (≥ 7.0 ± 1 mg l− 1 DO) using aeration pump. The addition of NSA in CWs enhanced the persistence and metabolic functioning of the inoculated bacteria in the water, rhizospheric soil, and plants. The maximum hydrocarbon removal (97%) was observed in the water treated by CWs having C. laevigatus, bacteria, and NSA, and it is correlated with the copy numbers of alkB and its expression level. The application of NSA in CWs not only improved bacterial persistence and catabolic gene expression but also increased plant development and hydrocarbon removal.

In vitro and in silico evaluation of anti-quorum sensing activity of marine red seaweeds-Portieria hornemannii and Halymenia dilatata

The bacterial cell communicates from one cell to another by binding Auto-Inducers to specific receptors and their virulence factors, which are all products of their expression system. Therefore, this pathogenesis is controlled by disrupting the signal-response system. The current study assesses three maritime red seaweeds, including Portieria hornemannii and Halymenia dilatata, for their anti-Quorum Sensing (QS) activity against four bacteria. Those opportunistic pathogens cause severe QS-dependent biofilm formation and other virulences. In vitro, the study showed that biofilm formation in S. aureus was inhibited with 43.3%, 55% in Acinetobacter sp, 48% in E. coli, and 39. 2 % in K. pneumoniae by red seaweed extracts. The EPS production was also highly inhibited in Acinetobacter sp. with 41 % more than other bacteria. The efflux pump expressions and QS-dependent swimming motility were also effectively reduced. The present study targets the receptor proteins to prevent from binding of QS signals. Correspondingly, the in silico research predicts the binding affinity of bioactive compounds of seaweed extracts to the QS receptor proteins. The Hexamethyl Cyclotrisiloxane, Benzo[h]quinoline, 2,4-dimethyl, and 5-Methyl-2-phenylindolizine compounds from H. dilatata, P. hornemannii, respectively, showed a higher binding affinity with receptor proteins such as AgrC (PDB ID: 4BXI) of S. aureus, SdiA (PDB ID:4LFU) of E. coli, Modelled SdiA protein of K. pneumoniae and Modelled AbaR protein of Acinetobacter sp. This study demonstrates the potential of seaweed against virulence and antibiotic resistance of pathogenic bacteria.

The extremophilic Andean isolate Acinetobacter sp. Ver3 expresses two ferredoxin-NADP+ reductase isoforms with different catalytic properties.

Ferredoxin/flavodoxin-NADPH reductases (FPRs) catalyze the reversible electron transfer between NADPH and ferredoxin/flavodoxin. The Acinetobacter sp. Ver3 isolated from high-altitude Andean lakes contains two isoenzymes, FPR1ver3 and FPR2ver3. Absorption spectra of these FPRs revealed typical features of flavoproteins, consistent with the use of FAD as a prosthetic group. Spectral differences indicate distinct electronic arrangements for the flavin in each enzyme. Steady-state kinetic measurements show that the enzymes display catalytic efficiencies in the order of 1-6 μm-1·s-1, although FPR1ver3 exhibited higher kcat values compared to FPR2ver3. When flavodoxinver3 was used as a substrate, both reductases exhibited dissimilar behavior. Moreover, only FPR1ver3 is induced by oxidative stimuli, indicating that the polyextremophile Ver3 has evolved diverse strategies to cope with oxidative environments.

Cellulolytic and Ethanologenic Evaluation of Heterotermes indicola's Gut-Associated Bacterial Isolates.

Cellulose is the basic component of lignocellulosic biomass (LCB) making it a suitable substrate for bioethanol fermentation. Cellulolytic and ethanologenic bacteria possess cellulases that convert cellulose to glucose, which in turn yields ethanol subsequently. Heterotermes indicola is a subterranean termite that causes destructive damage by consuming wooden structures of infrastructure, LCB products, etc. Prospectively, the study envisioned the screening of cellulolytic and ethanologenic bacteria from the termite gut. Twenty six bacterial strains (H1-H26) based on varied colonial morphologies were isolated. Bacterial cellulolytic activity was tested biochemically. Marked gas production in the form of bubbles (0.1-4 cm) in Durham tubes was observed in H3, H7, H13, H15, H17, H21, and H22. Sugar degradation of all isolates was indicated by pink to maroon color development with the tetrazolium salt. Hallow zones (0.42-11 mm) by Congo red staining was exhibited by all strains except H2, H7, H8, and H19. Among the 26 bacterial isolates, 12 strains were identified as efficient cellulolytic bacteria. CMCase activity and ethanol titer of all isolates varied from 1.30 ± 0.03 (H13) to 1.83 ± 0.01 (H21) umol/mL/min and 2.36 ± 0.01 (H25) to 7.00 ± 0.01 (H21) g/L, respectively. Likewise, isolate H21 exhibited an ethanol yield of 0.40 ± 0.10 g/g with 78.38 ± 2.05% fermentation efficiency. Molecular characterization of four strains, Staphylococcus sp. H13, Acinetobacter baumanni H17, Acinetobacter sp. H21, and Acinetobacter nosocomialis H22, were based on the maximum cellulolytic index and the ethanol yield. H. indicola harbor promising and novel bacteria with a natural cellulolytic tendency for efficient bioconversion of LCB to value-added products. Hence, the selected cellulolytic bacteria can become an excellent addition for use in enzyme purification, composting, and production of biofuel at large.

Changes of MRGs and ARGs in Acinetobacter sp. SL-1 used for treatment of Cr(VI)-contaminated wastewater with waste molasses as carbon source

Antibiotic resistance genes (ARGs) may be synergistic selected during bio-treatment of chromium-containing wastewater and causing environmental risks through horizontal transfer. This research explored the impact of self-screening bacterium Acinetobacter sp. SL-1 on the treatment of chromium-containing wastewater under varying environmental conditions. The findings indicated that the optimal Cr(VI) removal conditions were an anaerobic environment, 30 °C temperature, 5 g/L waste molasses, 100 mg/L Cr(VI), pH = 7, and a reaction time of 168 h. Under these conditions, the removal of Cr(VI) reached 99.10 %, however, it also developed cross-resistance to tetracycline, gentamicin, clarithromycin, ofloxacin following exposure to Cr(VI). When decrease Cr(VI) concentration to 50 mg/L at pH of 9 with waste molasses as carbon source, the expression of ARGs was down regulated, which decreased the horizontal transfer possibility of ARGs and minimized the potential environmental pollution risk caused by ARGs. The study ultimately emphasized that the treatment of chromium-containing wastewater with waste molasses in conjunction with SL-1 not only effectively eliminates hexavalent chromium but also mitigates the risk of environmental pollution.

Adhesion preference of the sticky bacterium Acinetobacter sp. Tol 5.

Gram-negative bacterium Acinetobacter sp. Tol 5 exhibits high adhesiveness to various surfaces of general materials, from hydrophobic plastics to hydrophilic glass and metals, via AtaA, an Acinetobacter trimeric autotransporter adhesin Although the adhesion of Tol 5 is nonspecific, Tol 5 cells may have prefer materials for adhesion. Here, we examined the adhesion of Tol 5 and other bacteria expressing different TAAs to various materials, including antiadhesive surfaces. The results highlighted the stickiness of Tol 5 through the action of AtaA, which enabled Tol 5 cells to adhere even to antiadhesive materials, including polytetrafluoroethylene with a low surface free energy, a hydrophilic polymer brush with steric hindrance, and mica with an ultrasmooth surface. Single-cell force spectroscopy as an atomic force microscopy technique revealed the strong cell adhesion force of Tol 5 to these antiadhesive materials. Nevertheless, Tol 5 cells showed a weak adhesion force toward a zwitterionic 2-methacryloyloxyethyl-phosphorylcholine (MPC) polymer-coated surface. Dynamic flow chamber experiments revealed that Tol 5 cells, once attached to the MPC polymer-coated surface, were exfoliated by weak shear stress. The underlying adhesive mechanism was presumed to involve exchangeable, weakly bound water molecules. Our results will contribute to the understanding and control of cell adhesion of Tol 5 for immobilized bioprocess applications and other TAA-expressing pathogenic bacteria of medical importance.

AraC transcriptional regulator, aspartate semialdehyde dehydrogenase and acyltransferase: Three putative genes in phenol catabolic pathway of Acinetobacter sp. Strain DF4

The objective of this study was to identify genes associated with the biodegradation of phenol by Acinetobacter sp. strain DF4 through the use of differential display (DD) methodology. The bacteria were grown in YEPG medium, and total RNA was extracted and analyzed using labeled primers to detect gene expression differences. Three distinctively expressed cDNA bands (ph1, ph2, and ph3) were identified, cloned, and sequenced. DNA analysis involved searching for open reading frames (ORFs), verifying results with the NCBI database, predicting promoter regions, and constructing phylogenetic trees using bioinformatics tools. The ph1 gene displayed a 97% identity with the AraC transcriptional regulator, suggesting its potential role in regulating the ortho-catabolic pathway of phenol. The ph2 gene showed a 98% identity with aspartate semialdehyde dehydrogenase, which is involved in phenol degradation. The ph3 gene had a 93% identity with acetyltransferase. Essential transcription factors, such as TATA, GTGTGT, CACA, and CTTTT, were detected, and the three genes promoter regions were predicted. This study successfully identified functional genes involved in the metabolism of cyclic chemicals, particularly phenol, using the DD technique. These findings provide insights into the biodegradation pathways of phenol by Acinetobacter sp. Strain DF4 and may contribute to the development of more efficient bioremediation strategies for phenol-contaminated environments.

Sulfadiazine and Nitrogen Removal Performance and Mechanisms of a Saline-Resistant Strain of Acinetobacter sp. RT-6

The main goal of this article is to elucidate the SDZ and TN removal characteristics and mechanisms of a saline-resistant strain of Acinetobacter sp. RT-6. The SDZ and TN removal characteristics indicated that SDZ and TN removal were significantly affected by SDZ concentration and salinity. The removal curves and kinetics of different typical amounts of nitrogen showed the shortcut nitrification and denitrification present in the ammonia-N removal process; the nitrogen-containing compound was mainly transformed into N2, and approximately 19.05 ± 0.83 mM of the electrons was transferred to the nitrate respiratory chain. The intermediates of SDZ degradation were identified, and it was speculated that the main reaction sites for SDZ transformation were the N–C bond, N–S bond, pyrimidine ring, and benzene ring.

Acinetobacter - A Hard to Treat Resilient ICU Pathogen

Objective: To isolate Acinetobacter sp and identify MDR (multidrug resistant) and XDR (extensively drug resistant) isolates from intensive care unit in a tertiary care hospital, Lahore. Methodology: This cross-sectional research was performed retrospectively in a tertiary care hospital, Lahore from January 2022-December 2022. It consisted of 435 specimens from ICU patients processed for culture and sensitivity in microbiology section of Pathology Laboratory, SMCH. The specimens included blood, pus, urine, cerebrospinal fluid, and other body cavity fluids, sputum, bronchial aspirates, wound swabs, ETT, etc. The specimens were cultured on Blood agar (Oxoid UK) and Mac Conkey agar (Oxoid UK) but CLED agar (Oxoid UK) was used for urine. After overnight incubation at 37°C, Acinetobacter sp were identified by morphology and biochemical reactions using Analytical profile index (API) 20 NE (Biomerieux, France). Results: One hundred and seventy-five cases revealed Gram negative bacteria (GNB) and 31 (17.71%) of the GNB were Acinetobacter sp. Fifteen isolates of Acinetobacter sp were obtained from respiratory secretions,7 from pus, 6 from urine, 2 from ETT, and 1 isolate from blood sample. A total of 31 isolates were obtained. Thirteen (41.9%) Acinetobacter isolates were MDR and 9 (29.0%) turned out to be XDR. The remaining 9 isolates exhibited satisfactory susceptibility. Conclusion: Acinetobacter sp. is responsible for a significant bulk of drug resistant ICU associated infections and is increasingly developing resistance as evident by 41.9% MDR and 29.0% XDR isolates.

Enhancement of gaseous chlorobenzene biodegradation and power generation in a microbial fuel cell by bifunctional Acinetobacter sp. HY-99C

The efficient biodegradation of volatile chlorinated hydrocarbons using microbial fuel cells (MFCs) offers a feasible approach for purifying waste gas and alleviating energy crises. However, power generation is limited by poor pollutant biodegradation and slow electron transfer. The bifunctional bacterium Acinetobacter sp. HY-99C was screened and used to improve the performance of a conventional MFC. The inoculation of strain HY-99C into the conventional MFC promoted the formation of a compact biofilm with high metabolic activity and an enriched bifunctional genus (Acinetobacter), which resulted in the accelerated decomposition of chlorinated aromatic compounds into biodegradable organic acids. This led to efficient chlorobenzene removal and power generation from the MFC, with a chlorobenzene elimination capacity of 70.8 g m−3 h−1 and power density of 89.6 mW m−2, which are improved over those of previously reported MFCs. This study provides novel insights into enhancing pollutant removal and power generation in MFCs.

Interaction of Acinetobacter sp. RIT 592 induces the production of broad-spectrum antibiotics in Exiguobacterium sp. RIT 594.

Antimicrobial resistance (AMR) is one of the most alarming global public health challenges of the 21st century. Over 3 million antimicrobial-resistant infections occur in the United States annually, with nearly 50,000 cases being fatal. Innovations in drug discovery methods and platforms are crucial to identify novel antibiotics to combat AMR. We present the isolation and characterization of potentially novel antibiotic lead compounds produced by the cross-feeding of two rhizosphere bacteria, Acinetobacter sp. RIT 592 and Exiguobacterium sp. RIT 594. We used solid-phase extraction (SPE) followed by liquid chromatography (LC) to enrich antibiotic extracts and subsequently mass spectrometry (MS) analysis of collected fractions for compound structure identification and characterization. The MS data were processed through the Global Natural Product Social Molecular Networking (GNPS) database. The supernatant from RIT 592 induced RIT 594 to produce a cocktail of antimicrobial compounds active against Gram-positive and negative bacteria. The GNPS analysis indicated compounds with known antimicrobial activity in the bioactive samples, including oligopeptides and their derivatives. This work emphasizes the utility of microbial community-based platforms to discover novel clinically relevant secondary metabolites. Future work includes further structural characterization and antibiotic activity evaluation of the individual compounds against pathogenic multidrug-resistant (MDR) bacteria.

Characterization of As(III)-oxidizing bacteria Acinetobacter sp. TMKU7 having plant growth promoting features for possible application in arsenic-contaminated crop field

Arsenic pollution is considered as one of the global environmental threats. Arsenic is found in nature mostly in two different valence states, namely arsenite [As(III)] and arsenate [As(V)], the former is more toxic due to its solubility and reactivity. Certain microbial communities inhabiting in the As-rich environment contribute a lot in the geochemical cycling of As. This study focuses on the isolation and identification of As(III) oxidizing bacteria from soil sample, and furthermore assessment of its As(III) transforming potential. The study was also aimed to hunt its plant growth promoting features for possible application to promote crop yield As-contaminated soil. Among the 28 bacterial isolates, a strain designated as TMKU7 could transform ∼80% As(III) to As(V) under culture condition. Based on morphological, biochemical, and molecular characterization, the strain was identified as Acinetobacter sp. Arsenite oxidase, the key player for As(III) to As(V) conversion was found to be constitutive in this strain, and the enzymatic activity was mostly found in the periplasmic fraction. The K m and V max of the partially purified As(III) oxidase were determined to be 41.43 μM and 0.19 μM min−1 μg−1 protein, respectively. The presence of As(III) oxidase gene (aioA) in the genomic DNA was further confirmed by PCR amplification. Agarose entrapped partially purified enzyme showed a potential for As(III) removal from water as well. The expression of various plant growth promoting traits have added additional importance to this As-resistant strain, which could be utilized as a prospective As-detoxification candidate in the As-contaminated crop field for sustainable agriculture.

Photoinduced promiscuity of cyclohexanone monooxygenase for the enantioselective synthesis of α-deuterated carbonyl compounds

The direct asymmetric synthesis of deuterium compounds has gained increasing attention. Here we report the engineered cyclohexanone monooxygenase from Acinetobacter sp. NCIMB 9871 for the synthesis of chiral α-deuterated carbonyl compounds via enantioselective reductive dehalogenation. The engineered CHMO exhibited good chemoselectivity, stereoselectivity and d-incorporation (up to 92% yield, 98% e.e. and 96% d-incorporation) toward a series of α-halogen carbonyl compounds. This method was also used for the synthesis of deuterated drugs, which demonstrated its promising application in synthetic chemistry.

An examination of the carbon metabolic pathways in Acinetobacter sp. TAC-1 in the context of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) utilization

The present study aimed to unravel the carbon metabolism pathway of Acinetobacter sp. TAC-1, a heterotrophic nitrification-aerobic denitrification (HN-AD) strain that utilizes poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) as a carbon source. Sodium acetate was employed as a control to assess the gene expression of carbon metabolic pathways in the TAC-1 strain. The results of genome sequencing demonstrated that the TAC-1 strain possessed various genes encoding carbon metabolic enzymes, such as gltA, icd, sucAB, acs, and pckA. KEGG pathway database analysis further verified the presence of carbon metabolism pathways, including the glycolytic pathway (EMP), pentose phosphate pathway (PPP), glyoxylate cycle (GAC), and tricarboxylic acid (TCA) cycle in the TAC-1 strain. The differential expression of metabolites derived from distinct carbon sources provided further evidence that the carbon metabolism pathway of TAC-1 utilizing PHBV follows the sequential process of PHBV (via the PPP pathway)→gluconate (via the EMP pathway)→acetyl-CoA (entering the TCA cycle)→CO2+H2O (generating electron donors and releasing energy). This study is expected to furnish a theoretical foundation for the advancement and implementation of novel denitrification processes based on HN-AD and solid carbon sources.

A Retrospective Case-Control Study of Eravacycline for the Treatment of Carbapenem-Resistant Acinetobacter Infections in Patients With Burn Injuries.

Thermal injuries lead to a deficiency in one's natural, protective barrier, resulting in increased susceptibility to pathogens, and often require multiple courses of broad-spectrum antibiotics. Eravacycline (ERA) has shown adequate in vitro activity against multiple multi-drug resistant (MDR) pathogens including Acinetobacter sp. Due to the increasing prevalence of MDR bacteria and the heightened susceptibility of patients with burns to infection, studies are needed to examine the clinical effect of eravacycline in this population. The objective of this retrospective, case-control study was to compare the outcomes of patients with thermal injuries treated with eravacycline versus a matched control for carbapenem-resistant Acinetobacter baumannii (CRAB) infections. Patients with thermal injury admitted to an American Burn Associated-verified burn center from May 1, 2019 to July 31, 2022, who received eravacycline, were randomly matched 4:1 to a historical cohort using a previously established, de-identified dataset of patients treated with colistimethate sodium (CMS) in the same burn center (March 1, 2009 to March 31, 2014), based on % total body surface area (%TBSA), age, and CRAB. A composite favorable outcome was defined as 30-day survival, completion of the course, lack of 14-day recurrence, and lack of acute kidney injury (AKI). Treatment with eravacycline over CMS was not more or less likely to be associated with a favorable response [odds ratio (95% confidence interval), 2.066 (0.456-9.361), P = .347]. Patients treated with CMS had nearly 9-fold higher odds of new-onset AKI versus ERA [8.816 (0.911-85.308), P = .06]. Adverse events were uncommon in the ERA group. There was no difference in mortality.

Removal of iron, manganese and ammonium from contaminated mine water by biochar immobilized Acinetobacter sp. AL-6 under acid condition, and the role of extracellular polymeric substances

In acidic mine wastewater, Mn and Fe are among the prime heavy metals and pose a great threat to the ecological environment and human health. Combining biological and physical methods to treat heavy metal contaminated water bodies is a promising remediation technique. In this study, grapefruit peel biochar immobilized Acinetobacter sp. AL-6 (co-system) was applied to treat the contaminated water with co-existing Mn2+, Fe2+ and NH4+-N. The results showed that almost 100% of Mn2+, Fe2+, Zn2+ and Cu2+ were removed in bioreactor, and was transferred to Mn2+, Fe3+, Zn2+ and Cu2+ precipitates on the surface of co-system without N2O accumulation. Especially, Mn2+ and Fe2+ were adsorbed in extracellular polymers (EPS) of strain AL-6. The present study mainly confirmed that the combined system of biochar and bacteria had great potential in the complex water removal of multiple heavy metals and NH4+-N, and also revealed the regulation of heavy metals by the EPS of strain.

Copper / Chitosan Nanocomposite Prepared by Chemical Method for Active Antimicrobial Activity

Background: Chitosan is a promising polymeric that has received much attention recently. Chitosan nanoparticles have wide applications as a nanocarrier for different organic and inorganic substances. Materials and Methods: In the present study, copper (CuNPs), chitosan nanoparticles (CNPs) and Cu/CS nanocomposite (Cu/CNC) were prepared and characterized. All prepared nanoparticles were inspected by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscope (FE-SEM ), Energy Dispersive Spectroscopy (EDS), UV/VIS spectroscopy, and zeta potential. Finally, the antimicrobial activity of CuNPs, CNPs and Cu/CNC was tested by disc diffusion assay at different concentrations (0.5-2 mg/ml) against Candida albicans, Klebsiella. pneumoniae , Pseudomonas aeruginosa , Proteus mirabilis , Cryptococcus sp. , Staphylococcus aureus, Escherichia coli, and Acinetobacter sp. Results: The results showed an absorbance peak at 550 nm due to the presence of Cu/CNC. From the FTIR spectrum, a peak at 686.66 cm-1 refers to the copper successfully binding with chitosan. Furthermore, the particle size average of Cu/CNC was 36.34 - 48.27 Cu/CNC has the highest growth inhibition zone at a concentration of 2 mg/ml against C.albicans, P.aeruginosa and S.aureus with the diameters (9.75±0.35, 15±1.41, 15.5±0.70) mm, respectively. Conclusion: This study showed that Cu/CNC has higher antimicrobial activity than CNPs and CuNPs. It presented higher antibacterial activity against gram-negative bacteria than gram-positive bacteria. Keywords: Copper nanoparticles, Chitosan nanoparticles, nanocomposite, XRD, FE_SEM Antimicrobial activity.

Complex secondary structure in small Rep_3 plasmids of Acinetobacter spp.

Bacterial plasmids are important mobile genetic elements which often carry specific genes important for bacterial successful survival under various inhospitable environmental conditions. Most of the previous research has focused on large plasmids providing these beneficial traits to their host cells. In this study, small cryptic plasmid pALK1 (3 051 bp) was isolated from metallotolerant and alkalitollerant strain Acinetobacter sp. K1. The plasmid encodes Rep_3 family replication protein and MobM mobilization protein but none pALK1-like plasmids were detected in other Acinetobacter strains of environmental and animal origin. The secondary structure of the pALK1 plasmid is characterized by the complexity of multiple sets of direct and inverted repeats in its nucleotide sequence. Comparative genomics was used to hypothesize the biological functions of these repeats in Acinetobacter spp., whereas several similar plasmids with a related organization of direct repeats and palindromes are known in this genus.

Optimising Wastewater Treatment: Acinetobacter sp. IrC1 as a potential multi-resistant bacterium for copper accumulation and dyes decolourisation.

Improper disposal of waste containing copper and dye is an environmental issue that must be resolved immediately due to its harmful, non-degradable and toxic properties. Bioremediation efficiency can improve by cultivating copper and dye multi-resistant bacteria to remove various pollutant types simultaneously. This study aims at establishing the multi-resistance of Acinetobacter sp. IrC1 to copper and dyes. The effects of copper concentration on growth were determined using a spectrophotometer, while accumulation was analysed using an atomic absorption spectrophotometer. Bacteria-mediated dye decolourisation dyes were observed based on clear zone formation around bacterial colonies, while decolourisation percentage was calculated using a spectrophotometer. Results demonstrate that Acinetobacter sp. IrC1 resisted up to 8 mM CuSO4 and accumulated up to 292.93 mg/g dry weight of copper cells. Acinetobacter sp. IrC1 isolates were also resistant to 500 ppm Methylene Blue, Malachite Green, Congo Red, Mordant Orange, Reactive Black, Direct Yellow, Reactive Orange, Remazol, Wantex Red and Wantex Yellow dye, successfully removing up to 68.35% and 79.50% Methylene Blue and Basic Fuchsine in a medium containing 3 mM CuSO4, respectively. Further investigations are required to analyse the genetic composition of multi-resistant bacteria to optimise the effectiveness of indigenous bacterial isolates as bioremediation agents.