Bacterial Growth Research Articles

A novel approach for microbial activity assessment in bioleaching. Towards to a standardised fast starting up protocol

Biohydrometallurgy is a proven industrial method for extracting base metals from sulfidic ores with low-grade content and as a pre-treatment of Au ores. The lack of study of biological aspects related with microbial activity assessment makes it difficult to control and monitor these processes; and the multitude of experimental procedures described in the literature hinders cross-study comparisons among researchers. Experimental tools that allow a quick and reliable quantitative assessment of the iron oxidising capacity of the cells during the bioleaching process are needed. This work proposes monitoring microbial activity through a simple and reliable method based on the offline measurement of the Oxygen Uptake Rate (OUR). The methodology allows to quantify the microbial activity evolution of a growing culture under no-limiting conditions. By this methodology, the maximum potential bioleaching rate of the culture at any time is determined, assessing the occurrence of a biological or chemical limitation. The results obtained reveals that whether due to Fe2+ or O2 depletion, substrate availability significantly limits microbial activity. This aspect is key to assess a culture suitability for bioleaching bioreactor inoculation, preventing long lag phases. Furthermore, the methodology allows for quick disturbances correction, avoiding process shutdowns and enhances technological reliability of continuous bioleaching.

The addition of humic acid into soil contaminated with microplastics enhanced the growth of black gram (Vigna mungo L. Hepper) and modified the rhizosphere microbial community.

Microplastics have polluted agricultural soils, posing a substantial risk to crop productivity. Moreover, the presence of microplastic pollution has caused a disturbance in the composition of the microbial community in the soil surrounding plant roots, therefore impacting the growth of beneficial bacteria. A study was conducted to examine if humic acid (HA) can counteract the harmful effects of microplastics (MPs) on the growth of black gram crops and the composition of the rhizosphere soil microbial community, to reduce the negative impacts of microplastics on these microorganisms and crops. The research was carried out using mud pots and the plastic utilized for the experiment consisted of 60% high-density polyethylene (HDPE) and 40% polypropylene (PP). The soil was enriched with lignite-based potassium humate, which had a pH range of 8.0-9.5 and with 65% humic acid. The experiment consisted of six treatments: T1, which served as the control without HA and MP; T2, which involved the use of HA at a concentration of 0.15% w/w; T3, which involved the use of MP at a concentration of 0.2% w/w; T4, which involved the use of MP at a concentration of 0.4% w/w; T5, which involved the combination of HA at a concentration of 0.15% w/w and MP at a concentration of 0.2% w/w; and T6, which involved the combination of HA at a concentration of 0.15% w/w and MP at a concentration of 0.4% w/w. The plant growth characteristics, including germination percentage, nodule number, and chlorophyll content, were measured. In addition, the DNA obtained from the rhizosphere soil was analyzed using metagenomics techniques to investigate the organization of the microbial population. Seedlings in soil polluted with MP exhibited delayed germination compared to seedlings in uncontaminated soil. Following 60days of growth, the soil samples treated with T5 (0.2% MP and 0.15% HA w/w) had the highest population of bacteria and rhizobium, with counts 5.58 ± 0.02 and 4.90 ± 0.02CFUg-1 soil. The plants cultivated in T5 had the most elevated chlorophyll-a concentration (1.340 ± 0.06mgg-1), and chlorophyll-b concentration (0.62 ± 0.02mgg-1) while those cultivated in T3 displayed the lowest concentration of chlorophyll-a (0.59 ± 0.02mgg-1) and chlorophyll-b (0.21 ± 0.04mgg-1). Within the phylum, Proteobacteria had the highest prevalence in all treatments. However, when the soil was polluted with MPs, its relative abundance was reduced by 8.4% compared to the control treatment (T1). Conversely, treatment T5 had a 3.76% rise in relative abundance when compared to treatment T3. The predominant taxa found in soil polluted with MP were Sphingomonas and Bacillus, accounting for 19.3% of the total. Sphingomonas was the predominant genus (21.2%) in soil polluted with MP and supplemented with humic acid. Humic acid can be used as a soil amendment to mitigate the negative effects of MPs and enhance their positive advantages. Research has demonstrated that incorporating humic acid into soil is a viable method for maintaining the long-term integrity of soil's physical, chemical, and biological characteristics.

Characterization and kinetics of whey protein isolate amyloid fibril aggregates under moderate electric fields

Food proteins solutions enable the controlled flow of electrical current when subjected to a Moderate electric field (MEF). This application results in internal heat generation, known as ohmic heating, accompanied by electrochemical reactions. These effects play a significant role in influencing the formation of protein amyloid fibril aggregates (AFA), which have broad applications in food and biomedical fields, ranging from improving food texture to biomedical applications such as drug delivery and disease treatment. This study focused on investigating the formation of β-Lactoglobulin (β-lg) AFA under MEF conditions using WPI as protein source and various characterization techniques (e.g., Thioflavin T fluorescence, circular dichroism, and electron microscopy). The results indicated that MEF prolonged the lag phase of AFA formation. Furthermore, nucleation and fibril growth showed higher activation coefficients and cooperativity level (n > 2) compared to conventional heating method. MEF treatment resulted in unique fibril clustering and the presence of unexpected higher-order AFA networks confirmed by electron microscopy. These findings highlight the significant role of MEF in influencing the aggregation kinetics of β-lg AFA. Exploring further into the electrochemical and thermal effects during protein aggregation processes holds the key to unlocking deeper insights fibril formation process.

Suppression of a transcriptional regulator, HexA, is essential for triggering the bacterial virulence of the entomopathogen, Xenorhabdus hominickii

A nematode-symbiotic bacterium, Xenorhabdus hominickii, exhibits two distinct lifestyles. Upon infection of its host nematode into a target insect, X. hominickii is released into the insect hemocoel and becomes pathogenic. This study examines the critical transformation in bacterial life forms concerning the activity of a transcriptional regulator, HexA. When X. hominickii was cultured in tryptic soy broth, HexA was expressed during the stationary phase of bacterial growth. Conversely, HexA was expressed in the early growth stage within the insect host, Spodoptera exigua, when infected with X. hominickii. The transient expression of HexA was succeeded by the expression of another transcriptional regulator, Lrp, which led to the production of bacterial virulent factors. Expression of HexA was manipulated by replacing its promoter with an inducible promoter controlled by the inducer, l-arabinose. In the absence of the inducer, the mutant bacteria expressed HexA at a low level, resulting in a bacterial culture broth that was more effective at suppressing insect immune responses than the wild type. When the inducer was added, HexA was expressed at high levels, rendering the culture broth ineffective in immunosuppression. Interestingly, expression of HexA inhibited the expression of another transcriptional regulator, Lrp, which in turn induced the expression of a non-ribosomal peptide synthetase, gxpS, leading to the production of an immunosuppressive metabolite, GXP. Suppression of HexA expression in mutant bacteria augmented GXP levels in secondary metabolites. This indicates that infection of X. hominickii into the insect host represses HexA expression and upregulates Lrp expression, leading to GXP production. The GXP metabolites inhibit insect immunity, thus protecting the bacteria-nematode complex. Therefore, the suppression of HexA expression in the insect hemocoel is crucial for the bacteria’s transition from a symbiotic to a pathogenic life form.

Epinephrine and norepinephrine regulate the expression of virulence factors in Gallibacterium anatis

Gallibacterium anatis is a member of the Pasteurellaceae family and is an opportunistic pathogen that causes gallibacteriosis in chickens. Stress plays a relevant role in promoting the development of pathogenicity in G. anatis. Epinephrine (E) and norepinephrine (NE) are relevant to stress; however, their effects on G. anatis have not been elucidated. In this work, we evaluated the effects of E and NE on the growth, biofilm formation, expression of adhesins, and proteases of two G. anatis strains, namely, the hemolytic 12656-12 and the nonhemolytic F149T biovars. E (10μM/mL) and NE (30 and 50μM/mL) increased the growth of G. anatis 12656-12 by 20% and 25%, respectively. E did not affect the growth of F149T, whereas 40μM/mL NE decreased bacterial growth by 25%. E and NE at a dose of 30-50μM/mL upregulated five fibrinogen adhesins in the 12565-12 strain, whereas no effect was observed in the F149T strain. NE increased proteolytic activity in both strains, whereas E diminished proteolytic activity in the 12656-12 strain. E and NE reduced biofilm formation (30%) and increased Congo red binding (15%) in both strains. QseBC is the E and NE two-component detection system most common in bacteria. The qseC gene, which is the E and NE receptor in bacteria, was identified in the genomic DNA of the 12565-12 and F149TG. anatis strains via PCR amplification. Our results suggest that QseC can detect host changes in E and NE concentrations and that catecholamines can modulate the expression of several virulence factors in G. anatis.

Extract from Psidium guineense Sw leaves: An alternative against resistant strains of Staphylococcus aureus

Psidium guineense SW., commonly known as sour guava, is used in traditional medicine to address diverse health issues, such as inflammation, infections, and gastrointestinal disorders. Although previous research has highlighted the antimicrobial properties of the root extract and the antioxidant potential of its fruits, information regarding the activities associated with the leaf extract is lacking. The aim of the study was to use the traditional knowledge of the biological properties of P. guineense and investigate its antimicrobial activity, mechanism of action, synergistic effects, and antivirulence activity against Staphylococcus aureus. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were determined for S. aureus, including antibiotic-resistant isolates. The synergy between the extract and antibiotics was evaluated. A growth curve was constructed for S. aureus treated with the extract. The anti-hemolytic activity was assessed by inhibiting hemolysis in human blood, and the inhibition of staphyloxanthin (STX) was examined. The extract effectively inhibited all strains with MIC and MBC values ranging from 256 to 512 µg/mL and 512 to 1024 µg/mL, respectively. Antimicrobial synergy experiments demonstrated the enhanced effectiveness of antibiotics, especially ciprofloxacin, when combined with the P. guineense extract, especially with ciprofloxacin, resulting in complete synergy against all S. aureus strains. In growth curve tests, the extract inhibited growth at MIC of 256 µg/mL within 8 h and significantly delayed it at MIC/2 (128 µg/mL) within 12 h. In antivirulence tests, the extract effectively reduced hemolysis and STX production by S. aureus at MIC and MIC/2, indicating its potential as an antimicrobial agent with antivirulence properties. The extract effectively inhibited S. aureus, including drug-resistant strains with low MIC and MBC values, exhibiting strong antimicrobial and synergistic properties with antibiotics. also In addition, the extract accelerated recovery by limiting bacterial growth and exhibiting antivirulence capabilities, reducing the severe symptoms of S. aureus infections.

Assessment and quantification of the microbial flora in the output water of two types of dental chairs: A comparative study

Objectives: Dental Unit Waterlines (DUWL) have shown to be a perfect host for different pathogenic microorganisms. The purpose of this study was to analyze and compare the level of bacterial contamination in the output water of 2 types of DUWL. Methods: Dental unit water samples from the air/water syringe of the A-dec (A-dec™ Performer 200, Newberg, USA) DUWL type and KaVo (ESTETICA™ E30/E70/E80 Vision, Kavo, Biberach, Germany) type were collected and analyzed for total aerobic flora, Pseudomonas aeruginosa, faecal coliforms, total coliforms, faecal streptococci and sulfite-reducing anaerobic flora. Results: The bacteriological analysis of water samples shows the presence of bacterial contamination at high levels exceeding the standard safety guidelines of 100 CFU/mL set up by the American Dental Association (ADA) and accepted by the Centers for Disease Control and prevention (CDC) on the heterotrophic bacterial load. The data shows no statistically significant differences for all bacteriological parameters studied between the conventional A-dec DUWL type and the KaVo type that has an automated mode of decontamination. Conclusions: Despite all the disinfecting solutions considered to eradicate the bacterial proliferation in DUWL, the problem remains one of the greatest challenges in modern dentistry. Practitioners and medical staff should not underestimate the harmful consequences of this bacterial growth, not only on the health of their patients but also on their own health.

Application of Irradiation in Food Preservation and Production

The Food irradiation is a tried-and-true technique that's frequently used to improve the quality and the safety of the meat. With the application of this technique, the growth of bacteria, viruses, and parasites is successfully inhibited.

A systematic study of sheep faeces to be used as an alternative inoculum source in the Hohenheim gas test

ABSTRACT In vitro studies of gas production (GP) using rumen fluid obtained from rumen-cannulated animals are common in feed evaluation for ruminants. The objective was to compare sheep faeces with rumen fluid from dairy cows as inocula in the Hohenheim gas test (HGT) using a large number of different-quality feeds. It then was evaluated whether GP obtained by using rumen inoculum (RI-GP) can be estimated from GP using faecal inoculum (FI-GP). Ninety feeds for ruminants including roughages (n = 27), total mixed rations (n = 6), commercial compound feeds for dairy cows (n = 18), cereal grains (n = 10), energy-rich by-products (n = 5), legume grains (n = 6), oilseed meals (n = 6), and other protein-rich feeds (n = 12) were incubated with either rumen inoculum (RI) or faecal inoculum (FI), and GP was recorded at 2, 4, 8, 12, 24, 48, and 72 h. Nonlinear equations were fitted to the GP data to determine GP kinetic parameters. Correlations between RI-GP and FI-GP were calculated for different time points. Linear regressions were calculated to estimate RI-GP from FI-GP using the entire data set or subsets of roughages and concentrates. GP kinetic parameters were lower for all feed categories when incubated with FI instead of RI. On average of all feed samples, the potential GP was 9 mL/200 mg dry matter (DM) lower and the rate of GP was 3.1%/h lower with FI than RI. The estimation of kinetic data for FI included a lag phase of 1.51 h on average, whereas no lag phase was estimated for RI. Estimated parameters indicated an overall lower fermentation activity of FI than RI. However, there was a very similar progression of GP curves of RI-GP and FI-GP. RI-GP after 24 h was significantly correlated with FI-GP in the time period of 24 to 60 h (r = 0.973 – 0.982, including all feed samples). Linear regression analysis showed that RI-GP after 24 h can be estimated from FI-GP after 24 h (Slope = 1.02, R2 = 0.97) and 48 h (Slope = 1.1, R2 = 0.97) including the complete data set. Splitting the data set into roughages and concentrate feeds did not lead to distinctly higher estimation accuracy. In conclusion, sheep faeces can be used as an alternative inoculum for studying a wide range of different-quality feedstuffs. The standard gas test may be modified without the need for rumen-cannulated animals.

Structure-Guided Discovery of a Potent Inhibitor of the Ferric Citrate Binding Protein FecB in Vibrio Bacteria.

Infections caused by Gram-negative bacteria present a significant risk to human health worldwide. Novel strategies are needed to deal with the challenge caused by drug-resistant bacteria. Here, we report a new approach to combat infections by targeting iron-binding proteins to suppress bacterial growth. We investigated the function of the conserved periplasmic binding protein FecB from Vibrio alginolyticus. FecB was known to play a crucial role in the bacterial growth and to relate with biofilm formation. We then solved the crystal structures and elucidated the binding mechanism of FecB with ferric ion chelated by citrate. The results indicated that FecB binds weakly to one citrate molecule and strongly to the Fe3+-(citrate)2 complex. Based on these results, a structure-based virtual screening approach was conducted against FecB to identify small molecules that block ferric citrate uptake. Further evaluations in vivo and in vitro demonstrated that salvianolic acid C significantly suppressed bacterial growth, indicating that targeting bacterial nutrient absorption is a promising strategy for identifying potential antibacterial drugs.

Structure‐Guided Discovery of a Potent Inhibitor of the Ferric Citrate Binding Protein FecB in Vibrio Bacteria

AbstractInfections caused by Gram‐negative bacteria present a significant risk to human health worldwide. Novel strategies are needed to deal with the challenge caused by drug‐resistant bacteria. Here, we report a new approach to combat infections by targeting iron‐binding proteins to suppress bacterial growth. We investigated the function of the conserved periplasmic binding protein FecB from Vibrio alginolyticus. FecB was known to play a crucial role in the bacterial growth and to relate with biofilm formation. We then solved the crystal structures and elucidated the binding mechanism of FecB with ferric ion chelated by citrate. The results indicated that FecB binds weakly to one citrate molecule and strongly to the Fe3+‐(citrate)2 complex. Based on these results, a structure‐based virtual screening approach was conducted against FecB to identify small molecules that block ferric citrate uptake. Further evaluations in vivo and in vitro demonstrated that salvianolic acid C significantly suppressed bacterial growth, indicating that targeting bacterial nutrient absorption is a promising strategy for identifying potential antibacterial drugs.

Effectiveness of co-cultured Myristica fragrans Houtt. seed extracts with commensal Staphylococcus epidermidis and its metabolites in antimicrobial activity and biofilm formation of skin pathogenic bacteria

BackgroundSkin commensal bacteria (Staphylococcus epidermidis) can help defend against skin infections, and they are increasingly being recognized for their role in benefiting skin health. This study aims to demonstrate the activities that Myristica fragrans Houtt. seed extracts, crude extract (CE) and essential oil (EO), have in terms of promoting the growth of the skin commensal bacterium S. epidermidis and providing metabolites under culture conditions to disrupt the biofilm formation of the common pathogen Staphylococcus aureus.MethodsThe culture supernatant obtained from a co-culture of S. epidermidis with M. fragrans Houtt. seed extracts in either CE or EO forms were analyzed using gas chromatography-mass spectrometry (GC-MS) and liquid chromatography tandem mass spectrometry (LC-MS/MS), in silico investigations, and applied to assess the survival and biofilm formation of S. aureus.ResultsThe combination of commensal bacteria with M. fragrans Houtt. seed extract either CE or EO produced metabolic compounds such as short-chain fatty acids and antimicrobial peptides, contributing to the antimicrobial activity. This antimicrobial activity was related to downregulating key genes involved in bacterial adherence and biofilm development in S. aureus, including cna, agr, and fnbA.ConclusionThese findings suggest that using the culture supernatant of the commensal bacteria in combination with CE or EO may provide a potential approach to combat biofilm formation and control the bacterial proliferation of S. aureus. This may be a putative non-invasive therapeutic strategy for maintaining a healthy skin microbiota and preventing skin infections.

Phytochemical Content towards Weak Antioxidants Activity of Traditional Fermented VCO as the Basic Ingredient for Ear Drops

Chronic Suppurative Media Otitis is caused by pathogenic bacteria, which, if the growth is not controlled, will cause meningitis and can lead to death. Virgin Coconut Oil is an oil made through the traditional fermentation process of coconut milk and can inhibit the growth of pathogenic bacteria that cause Chronic Suppurative Media Otitis. So far, pathogenic bacteria can be controlled using ear drops made from artificial chemicals, which can cause resistance. Only a few have studied the manufacture of natural-based ear drops from VCO. The purpose of this study is to study the potential of VCO as a natural essential ingredient for ear drops for patients with OMSK by analyzing its antioxidant content using the DPPH method and its phytochemical content using Ultraviolet-Visible Spectroscopy (UV-Vis) and Gas Chromatography-Mass Spectrometry (GC-MS). Its antioxidants in the IC50 (ppm) region are 583.92mg/L. The types of fatty acids contained in VCO consist of Medium-Chain Fatty Acid (MCFA), Long-Chain Fatty Acid (LCFA) and Very Long Chain Fatty Acid (VLCFA), the most of which is lauric acid (MCFA), as much as 49.28%. Conventional analysis of secondary metabolites showed the presence of Alkaloids, Terpenoids, Ascorbic Acid, and Saponins. It can be concluded that the chemical content of Virgin Coconut Oil made from fermentation can be used in the health field as a primary ingredient for making ear drops for CSOM patients.

Levels of IL-6 and IL-8 in complicated versus uncomplicated urinary tract infection

Background: Urinary tract infections (UTIs) are one of the world's most frequent infectious diseases, affecting 150 million people each year and resulting in severe morbidity and high medical expenditures. UTIs can be clinically defined as uncomplicated UTIs (uUTIs) or complicated UTIs (cUTIs) to differentiate infections of benign origin from those with a higher risk of recurrence or progression to severe pathology. The aim of this study was to evaluate interleukin-6 (IL-6) and IL-8 as potential biomarkers in differentiating complicated and uncomplicated Methods: Ninety samples of urine were collected. There were 43 samples from healthy controls and 47 samples from UTI patients, those who have been clinically diagnosed with UTIs by the urologist. The serum IL-6 and IL-8 were measured using an enzyme-linked immunosorbent assay and commercially available kits. Results: The levels of both IL-6 and IL-8 were significantly higher in UTI patient then in control subjects (p=0.001, p=0.001). A significant difference was observed in the mean of level IL-6 between culture positive UTI patients and culture negative UTI patients (p=0.014). In addition, the type of bacterial growth, a significant difference was observed in the mean of serum IL-6 and IL-8 level in UTI caused by gram negative bacteria in comparison with UTI caused by gram positive bacteria. Conclusion: High levels of IL-6 are associated with the growth of gram-negative bacteria, and this indicates that gram-negative bacteria could induce stronger inflammatory responses than gram-positive bacteria. IL-8 levels are higher in UTIs caused by gram-negative bacteria. This result further supported the evidence that gram-negative bacteria are potent inducers of inflammatory responses.

Formulation and Quality Analysis of Yoghurts Fortified with Mentha spicata, Moringa oleifera, and Murraya koenigii Leaf Extracts

The aim of this study was to investigate the impact of incorporating Mentha spicata (mint), Moringa oleifera (moringa), and Murraya koenigii (curry) leaf extracts into yoghurt to enhance its nutritional and therapeutic benefits. The study assessed the sensory, physicochemical, microbiological, and antibacterial properties of the fortified yoghurts along with control. Among the four yoghurt samples, curry leaf extract-fortified yoghurt has the fastest setting time (4.5 h), highest protein content (3.42%) and lowest syneresis (8%) and was the most preferred in sensory analysis, excelling in color, texture, and overall acceptability (p=0.05). It also showed the strongest antibacterial activity against Salmonella and Staphylococcus aureus. All yoghurt samples were found to be safe for consumption. The incorporation of leaf extracts significantly improved the growth of lactic acid bacteria, sensory qualities and functional benefits of yoghurt, making them promising ingredients for developing health-promoting beverages. However, there is a need for optimization when using these extracts to reduce its adverse taste effects, particularly at higher concentrations.

Adaptation to zinc restriction in Streptococcus agalactiae: role of the ribosomal protein and zinc-importers regulated by AdcR.

Streptococcus agalactiae is a bacterial human pathobiont causing invasive diseases in neonates. Upon infection, S. agalactiae is presented with Zn limitation and excess but the genetic systems that allow bacterial adaptation to these conditions remain largely undefined. A comprehensive analysis of S. agalactiae global transcriptional response to Zn availability shows that this pathogen manages Zn limitation mainly through upregulation of the AdcR regulon. We demonstrate that several AdcR-regulated genes are important for bacterial growth during Zn deficiency, including human biological fluids. Taken together, these findings reveal new mechanisms of S. agalactiae adaptation under conditions of metal deprivation.

Bacterial Co-Infections and Antibiotic Resistance in Urinary Tract Infection of Covid-19 Patients in Erbil City

The COVID-19 pandemic has raised concerns over secondary infections because it has limited treatment options and empiric antimicrobial treatment poses serious risks of aggravating antimicrobial resistance. Many studies have shown that COVID-19 patients are predisposed to developing secondary infections. The prevalence of urinary tract infections (UTI) was evaluated in 248 patients admitted to different hospitals in Erbil city, Iraq. Results showed 138 (55.65%) patients were positive for bacterial growth, of which 72 isolates of Gram-negative and 66 isolates of Gram-positive bacteria were isolated and identified from the urine of COVID-19 patients depending on the 16S rRNA gene using PCR. The predominant obtained bacteria were Staphylococci species, of which isolates belong to 6 species, and the predominant Gram-negative species was Pseudomonas spp. which belongs to 4 species. Also, their susceptibility to 15 antibiotics was tested and it was found that most of the Gram-negative isolates were highly resistant to ampicillin 66(91.66%), amoxicillin 60(83.33%), cephalexin 52(72.22%) and cefixime 50(69.44%). While the most effective antibiotic was imipenem, and with percentage of 26(36.11%), it also showed variable sensitivity to other antibiotics. For Gram-positive bacteria, the highest resistance was against cefixime 40(60.60%), ampicillin 28(42.42%), and 18(27.27%) for both amoxicillin and ciprofloxacin, while the most effective antibiotic was gentamicin, which showed effectiveness against all the Gram-positive isolates. Another part of the study concerned with detection of the existence of ESBLs genes responsible for antibiotic resistance. The results revealed that all the isolates possessed the 16S rRNA gene, whereas blaTEM and blaCTX-M were found to be the most possessed genes in all the isolates, with a percentage of (88.33%).

Novel structural determinants and bacterial death-related regulatory effects of the scorpion defensin BmKDfsin4 against gram-positive bacteria.

Numerous defensins constitute a family of cationic antimicrobial peptides with high degrees of sequence variability, and in-depth characterization of their structural basis and antibacterial mechanisms remains limited. Here, a representative scorpion defensin, BmKDfsin4, with two distinct hydrophobic and basic residue clusters, was extensively investigated. The hydrophobic residue cluster, formed by Phe2, Pro5, Phe6, Phe28 and Leu29 residues, strongly influences the antibacterial activity of BmKDfsin4 against Gram-positive bacteria. Compared with the three scattered Lys13, Lys30 and Arg32 residues, the basic residue cluster, consisting of the Arg19, Arg20, Arg21 and Arg37 residues, played a less important role. The synergistic interaction between the basic residue cluster and Arg32 significantly affected BmKDfsin4 function. The bacterial growth inhibition by BmKDfsin4 was associated with regulating expression levels of cell division-related genes, cell wall synthesis-related genes and bacterial autolysis-related genes rather than destroying the bacterial cell membrane. The coincubation of BmKDfsin4 with the bacterial strains induced gradual changes in the bacterial surface from a rough and thin surface to a noticeably wrinkled surface together with abundant white spots and even complete cavities within the bacteria. These findings revealed novel structural determinants and bacterial death-related regulatory effects of the defensin BmKDfsin4 and highlighted diverse antibacterial mechanisms of defensins.

Detection of the antibacterial role of Achillea millefolium against Escherichia coli isolated from urinary tract infections

Despite the fact that the pharmaceutical industry has developed numerous novel antibiotics over the last three decades, bacteria have developed resistance to these medications. Bacteria have the genetic potential to transfer and develop resistance to medications used as therapeutic agents. Therefore, the present study aimed to reveal the antibacterial role of Achillea millefolium against Escherichia coli isolated from urinary tract infections. Between February and July of 2024, 130 clinical samples were taken from individuals who were admitted to Kirkuk Hospital in Kirkuk City after visiting a specialist and being sent to the laboratory. Urine samples were taken from patients with UTI ranging in age from (1-60 years) of women, after which they were transferred directly to the laboratory to be cultured on the culture media, then A. millefolium extract was tested against Escherichia coli, compared with some standard antibiotics. Results showed that 57 (43.8%) of the total samples showed positive results for bacterial growth when cultured on the best culture media, which included blood and MacConkey agars. 73 (or 56.2%) of the total samples had results that showed no bacterial growth. E. coli showed total resistance (100%) to Ampicillin. While, a low sensitive toward Nalidixic acid (20.0%), Clindamycin (20.0%) 21.5%. Otherwise, E. coli showed a high sensitive to Gentamycin (87.7%), Imipenem (96.9%), and Amikacin (90.8%). While Tobromycin showed high sensitive 100.0% respectively. Based on the results, it was shown that the extract of A. millefolium at a dosage of 100 mg induced an inhibition diameter rate of 18.7±3.45, while at a concentration of 150 mg, it produced an inhibition diameter rate of 29.49±2.97. It is concluded from that the alcoholic extract of A. millefolium has an antibacterial effect and is very effective in treating cases of urinary tract infection resulting from infection with Escherichia coli.

Polydopamine-Mediated Antimicrobial Lipopeptide Surface Coating for Medical Devices.

Biofilm formation on medical implants such as catheters is a major issue which needs to be addressed as it leads to severe health care associated infections. This study explored the design and synthesis of a polydopamine-lipopeptide based antimicrobial coating. The coating was used to modify the surface of Ultrathane Catheters. The lipopeptide SL1.15 with an N-terminal cysteine was covalently conjugated to the polydopamine modified catheters via a Michael addition reaction between the thiol moiety in the peptide and the aromatic ring in the polydopamine layer. The immobilization of the peptide on the polydopamine coated catheters was confirmed using water contact angle, X-ray photoelectron spectroscopy, atomic force microscopy, and scanning electron microscopy (SEM). The antimicrobial activity of the coated catheters investigated using drug resistant and clinical strains of Gram-positive (MRSA and S. aureus) and Gram-negative (E. coli, A. baumannii, and P. aeruginosa) bacteria revealed that lipopeptide immobilization inhibited >90% bacterial adhesion to the catheter surface. Additionally, biofilm assays against MRSA and E. coli revealed that the lipopeptide immobilized catheters inhibited >85% bacterial growth after 1 week incubation. Finally, the cytotoxicity profile of the catheters using the human dermal fibroblast, and the human embryonic kidney cell lines demonstrated that the polydopamine-lipopeptide coating was not toxic after 72 h incubation.