Method for high-throughput antifungal activity screening of bacterial strain libraries

Biofilm-forming bacteria are sources of infections because they are often resistant to antibiotics and chemical removal. Recombinant biofilm-degrading enzymes have the potential to remove biofilms gently, but they can be toxic toward microbial hosts and are therefore difficult to produce in bacteria. Here, we investigated Nicotiana species for the production of such enzymes using the dispersin B-like enzyme Lysobacter gummosus glyco 2 (Lg2) as a model. We first optimized transient Lg2 expression in plant cell packs using different subcellular targeting methods. We found that expression levels were transferable to differentiated plants, facilitating the scale-up of production. Our process yielded 20 mg kg−1 Lg2 in extracts but 0.3 mg kg−1 after purification, limited by losses during depth filtration. Next, we established an experimental biofilm assay to screen enzymes for degrading activity using different Bacillus subtilis strains. We then tested complex and chemically defined growth media for reproducible biofilm formation before converting the assay to an automated high-throughput screening format. Finally, we quantified the biofilm-degrading activity of Lg2 in comparison with commercial enzymes against our experimental biofilms, indicating that crude extracts can be screened directly. This ability will allow us to combine high-throughput expression in plant cell packs with automated activity screening.

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Endosymbiotic Rickettsiella causes cytoplasmic incompatibility in a spider host

10.1101/2020.03.03.975581 ◽

2020 ◽

Author(s):

Laura C. Rosenwald ◽

Michael I. Sitvarin ◽

Jennifer A. White

Keyword(s):

Bacterial Community ◽

High Throughput ◽

Bacterial Strain ◽

High Throughput Sequencing ◽

Cytoplasmic Incompatibility ◽

The Other ◽

Bacterial Endosymbionts ◽

Different Strains

AbstractMany arthropod hosts are infected with bacterial endosymbionts that manipulate host reproduction, but few bacterial taxa have been shown to cause such manipulations. Here we show that a bacterial strain in the genus Rickettsiella causes cytoplasmic incompatibility (CI) between infected and uninfected hosts. We first surveyed the bacterial community of the agricultural spider Mermessus fradeorum (Linyphiidae) using high throughput sequencing and found that individual spiders can be infected with up to five different strains of maternally-inherited symbiont from the genera Wolbachia, Rickettsia, and Rickettsiella. The Rickettsiella strain was pervasive, found in all 23 tested spider matrilines. We used antibiotic curing to generate uninfected matrilines that we reciprocally crossed with individuals infected only with Rickettsiella. We found that only 13% of eggs hatched when uninfected females were mated with Rickettsiella-infected males; in contrast, at least 83% of eggs hatched in the other cross types. This is the first documentation of Rickettsiella, or any Gammaproteobacteria, causing CI. We speculate that induction of CI may be much more widespread among maternally-inherited bacteria than previously appreciated. Further, our results reinforce the importance of thoroughly characterizing and assessing the inherited microbiome before attributing observed host phenotypes to well-characterized symbionts such as Wolbachia.

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Elucidation and Identification of an Antifungal Compound from Pseudomonas aeruginosa DA3.1 Isolated from Soil in Vietnam

Jundishapur Journal of Microbiology ◽

10.5812/jjm.103792 ◽

2020 ◽

Vol 13 (10) ◽

Author(s):

Nguyen Thi Trung ◽

Nguyen Tien Cuong ◽

Nguyen Thi Thao ◽

Dao Thi Mai Anh ◽

Do Thi Tuyen

Keyword(s):

Nuclear Magnetic Resonance ◽

Pseudomonas Aeruginosa ◽

Antifungal Activity ◽

Carboxylic Acid ◽

Magnetic Resonance ◽

13C Nmr ◽

Bacterial Strain ◽

Antifungal Compound ◽

Fusarium Sp ◽

High Antifungal Activity

Background: Fusarium sp. and Rhizoctonia sp. fungi have been always threats to short-term crops. In Vietnam, corn and soybean suffer serious losses annually. Therefore, it is necessary to utilize an environmentally friendly antifungal compound that is highly effective against phytopathogenic fungi. Pseudomonas sp. is a popular soil bacterial strain and well known for its high antifungal activity. Objectives: This study was carried out to evaluate and assess the antifungal activity of a local bacterial strain namely DA3.1 that was later identified as Pseudomonas aeruginosa. This would be strong scientific evidence to develop an environmentally friendly biocide from a local microorganism strain for commercial use. Methods: The antifungal compound was purified from ethyl acetate extraction of deproteinized cell culture broth by a silica gel column (CH2Cl2/MeOH (0% - 10% MeOH)). The purity of the isolated compound was determined by HPLC, and its molecular structure was elucidated using spectroscopic experiments including one-dimensional (1D) (1H NMR, 13C NMR, DEPT) and two-dimensional (2D) (HMBC and HSQC) spectra. The activity of the purified compound against Fusarium sp. and Rhizoctonia sp. fungi was measured using the PDA-disk diffusion method, and its growth-promoting ability was evaluated using the seed germination test of corn and soybean. Results: The results showed that the antifungal compound produced by Pseudomonas aeruginosa DA3.1 had a retention factor (Rf) of 0.86 on thin layer chromatography (TLC). Based on the evidence of spectral data including proton nuclear magnetic resonance (1H NMR), carbon nuclear magnetic resonance (13C NMR), distortionless enhancement by polarization transfer (DEPT), heteronuclear multiple bond correlation (HMBC), and heteronuclear single quantum coherence (HSQC), the chemical structure was elucidated as phenazine-1-carboxylic. The purified compound showed inhibitory activity against F. oxysporum and R. solani and exhibited the ability of the germination of corn and soybean seeds. The results revealed the benefit of native P. aeruginosa DA3.1 and phenazine-1-carboxylic acid for use as a biocontrol agent, as well as a plant growth promoter. Conclusions: The antifungal compound isolated from local Pseudomonas DA3.1 was identified as phenazine-1-carboxylic acid that posed high antifungal activity and was a plant germination booster.

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Manganese (II) and Cobalt (II) Acetylacetonates as Antimicrobial Agents

NIGERIAN ANNALS OF PURE AND APPLIED SCIENCES ◽

10.46912/napas.43 ◽

2019 ◽

Vol 1 ◽

pp. 176-185

Author(s):

S G Yiase ◽

S O Adejo ◽

S T Iningev

Keyword(s):

Antimicrobial Activity ◽

Antifungal Activity ◽

Antimicrobial Agents ◽

Inhibitory Concentration ◽

Dilution Method ◽

Spectroscopic Techniques ◽

Metal Chlorides ◽

Activity Screening ◽

Antibacterial And Antifungal ◽

Broth Dilution

Mn(II) and Co(II) complexes were prepared by reaction of the metal chlorides with acetylacetone in ammonical aqueous medium. The metal complexes were prepared in order to investigate their antimicrobial activity on some selected pathogens. The characterisation of the complexes was on the basis of various spectroscopic techniques like infrared and ultraviolet studies. The compounds were subjected to antimicrobial activity screening using serial broth dilution method. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal/Fungicidal Concentration (MBC/MFC) were determined. Mn(II) complex has shown significantly both antibacterial and antifungal activity with a MIC of 1.25 μg/mL while Co(II) complex was noticeable for antifungal activity at the same concentration. Whereas Mn(II) acetylacetonate is a more potent bactericide while Co(II) acetylacetonate is a more potent fungicide, both with MBC/MFC value of 2.5 μg/mL. Antimicrobial agent of the ligand has enhanced on complexation with Mn(II) and Co(II) ions. Though, the potency of the prepared antibiotics on the tested microbes is less compared to the standard drugs (Ciprofloxacin and Fulcin).

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