Portrait of Aya Dweeb

Research

Researching antimicrobial activity from soil-derived actinomycetes

My master’s research explored agricultural soil as a source of actinomycetes capable of producing metabolites with antimicrobial activity.

The project combined environmental sampling, microbial isolation, antimicrobial screening, production optimization, scientific writing, and collaboration with external specialized laboratories.

Degrees

Academic Degrees

Master of Science in Microbiology

Menoufia University

Faculty of Science — Department of Botany and Microbiology

2021–2025Degree awardedAugust 2025

Thesis

Production of Antimicrobial Compound by Some Actinomycetes

Bachelor of Science — Special Degree in Microbiology

Tanta University

Faculty of Science — Department of Microbiology

2014–2018Overall gradeVery Good

Graduation research

Literature-based study on dermatophytes

Design

Research Design

  • Ten agricultural soil samples were collected from Ashmoun, Menoufia Governorate, Egypt
  • Samples were collected beside agricultural plants
  • Collection depth was approximately 15–20 cm
  • Twenty actinomycete isolates were obtained
  • All isolates demonstrated varying levels of antimicrobial activity
  • Two isolates showed activity against all six test microorganisms and were selected for further investigation

Test Microorganisms

  • Escherichia coli
  • Salmonella typhi
  • Pseudomonas aeruginosa
  • Staphylococcus aureus
  • Candida albicans
  • Penicillium marneffei

Isolates

Selected Isolates

  1. 01

    Isolate No. 10

    Streptomyces rochei ASN

    Isolate No. 10 demonstrated broad-spectrum antimicrobial activity.

    It was identified externally using:

    • 16S rDNA sequencing
    • Phylogenetic analysis

    Its sequence was deposited in GenBank under accession number: GenBankPQ673648

    Main Findings

    • Activity increased with longer incubation
    • Peak activity was reached after eight days
    • Cell-free supernatant demonstrated dose-dependent antimicrobial activity
    • S. aureus, C. albicans, and P. marneffei were among the most susceptible organisms
    • Starch was the most effective carbon source
    • Sodium nitrate was the most effective nitrogen source
    • Incubation at 25°C supported maximum production

    The complete published study also included molluscicidal, parasitology, histological, and scanning-electron-microscopy findings performed through external specialized laboratories.

  2. 02

    Isolate No. 20

    Streptomyces sp.

    The second selected isolate showed strong broad-spectrum activity but could not be assigned a final consistent molecular species identification.

    Different laboratories produced inconsistent amplification and sequence-matching outcomes. It was therefore reported conservatively as Streptomyces sp.

    Optimal production conditions included:

    • Starch as the carbon source
    • Sodium nitrate as the nitrogen source
    • Neutral pH 7
    • Incubation at 25°C
    • Peak activity after eight days

    At an 80% cell-free-supernatant concentration:

    • 94.7% inhibition was recorded against Staphylococcus aureus
    • 91.48% inhibition was recorded against Penicillium marneffei

    External SEM analysis reported severe structural damage, including cell-wall degradation and fungal-hypha collapse.

Contribution

My Direct Contribution

I personally performed or contributed directly to:

  • Soil-sample collection
  • Actinomycete isolation
  • Purification
  • Pure-culture preparation and preservation
  • Gram staining
  • Microscopic examination
  • Antimicrobial screening
  • Agar-based assays
  • Measurement of inhibition zones
  • Microbial-suspension preparation
  • Cell-free-supernatant preparation
  • Centrifugation and membrane filtration
  • Production-condition optimization
  • Comparison of growth media
  • Carbon- and nitrogen-source evaluation
  • Time- and temperature-condition evaluation
  • Experimental-data recording
  • Preparation of tables and figures
  • Thesis writing
  • Original manuscript-draft writing
  • Revision following supervisor feedback
  • Preparation of samples for external analysis

I did not personally perform:

  • Genetic sequencing
  • Phylogenetic analysis
  • Parasitology experiments
  • Molluscicidal experiments
  • SEM imaging
  • Specialized histological examinations

Problem-solving

Research Problem-Solving

Contamination was one of the main practical challenges.

To reduce the risk of losing important isolates, I:

  • Prioritized time-sensitive experiments
  • Completed experiments while cultures remained pure
  • Maintained pure cultures
  • Preserved copies in more than one laboratory
  • Avoided dependence on a single storage location
  • Coordinated specialized external laboratory work when advanced facilities were unavailable at the university

Publications

Scientific Publications

  1. 01

    International Publication

    Elfeky, N., Abd Elsalam, A., El-Sabbagh, S., & Abdel-Motleb, A. (2025).

    “Antimicrobial and molluscicidal activities of Egyptian soil-derived Streptomyces rochei.”

    AMB Express, 15, Article 125.

    DOI10.1186/s13568-025-01927-0

    Authorship positionSecond author

  2. 02

    Local Scientific Publication

    “Harnessing Streptomyces sp. for Novel Antibiotics: Optimization, SEM Characterization, and Broad-Spectrum Activity.”

    Egyptian Academic Journal of Biological Sciences, G. Microbiology, 17(1), 163–176, 2025.

    DOI10.21608/eajbsg.2025.430202

    Authorship positionSecond author

Defense

Thesis Defense

I successfully defended my master’s thesis in August 2025.

The defense was conducted entirely in English and included:

  • The research problem
  • Research methodology
  • Practical experiments
  • Scientific images
  • Tables
  • Quantitative results
  • Questions from the examination committee

Accuracy

Scientific Accuracy