Isolation and Characterization of Magnetotactic Bacteria Collected from Northern India: A Preliminary Study

Screening, Isolation and Characterization of Aerobic Magnetotactic Bacteria From Western Ghats Forest Soil

Magnetotactic bacteria (MTB) are a unique ecophysiological group of iron-metabolizing bacteria that have immense potential biotechnological applications. These bacteria have predominantly been isolated from oxygen-limited conditions of aquatic niches and rarely from the soils. The Western Ghats biodiversity hotspot has been well-studied for its fauna and flora diversity. The present study includes optimization of enrichment medium for cultivation of MTB, to suit aerobic mesophiles from forest soil. The major components included were Ferric quinate and Resazurin. The enrichment and isolates were characterized for their magnetic properties using magnetotaxis on agar plates, Vibrating Sampler Magnetometer (VSM), and X-ray diffraction (XRD) analysis. The isolates, namely Bacillus sp. S1 (MN212953), Sphingoaurantiacus sp. S2_03 (MN212954), Burkholderia sp. S2_08 (MN212955) and Microvirga sp. S2_09 (MN212956) were isolated and characterized to have a magnetosome size of 2.5-8 nm. Our study is the first report on the enrichment and isolation of MTB from Western Ghats forest soil.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-024-01316-4.

Production and characterization of naturally occurring antibacterial magnetite nanoparticles from magnetotactic Bacillus sp. MTB17

AIMS

This study envisaged the isolation and characterization of magnetite nanoparticles (MNPs) from magnetotactic bacteria (MTB) and the evaluation of their antibacterial efficacy.

METHODS AND RESULTS

MNPs were extracted from 20 motile but morphologically different MTB, and they were subjected to antibacterial activity assay. These MNPs were found to be highly effective against Vibrio cholerae. MTB17 was considered as the potent MTB strain based on the antibacterial activity. The MNPs of MTB17 were isolated and validated by UV-Visible spectroscopy, particle size analysis, FTIR analysis, and PXRD.

CONCLUSIONS

Isolation and characterization of ~85 nm MNPs from MTB is reported, and it is highly active against all the gram-positive and gram-negative strains tested.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study focuses on a novel use of biogenic magnetite MNPs as an antibacterial agent, which can be further explored using in vivo studies.

Metal biosorption by magnetotactic bacteria isolated from fresh water sediments and characterization of extracted magnetosomes

The focus of the present study is to isolate and identify magnetotactic bacteria from fresh water sediments in Salem region, Tamil Nadu. Fresh water sediments were collected and characterized by X-ray diffraction to detect the crystalline nature of particles. Totally 12 isolates were screened for the metal biosorption efficiency in modified nutrient agar plates with 10 mg (lower concentration) of four different metals viz., manganese chloride, zinc sulphate, copper sulphate and potassium dichromate. Followed by testing their ability to tolerate higher concentration of metals viz., 20 mg, 30 mg, 50 mg, 70 mg, 90 mg and 150 mg/50 ml was analyzed. Only four bacteria survived the highest concentration of manganese and zinc (3000 µg/ml), CuSO₄ and K₂Cr₂O₇ at a concentration of 1400 µg/ml and 1800 µg/ml, respectively. The four bacterial strains Stenotrophomonas maltophilia, two Pseudomonas aeruginosa strains and Achromobacter xylosoxidans were grown in modified nutrient broth (NB) and Luria Bertani (LB) incorporated with metals such as manganese, zinc, copper and chromium and tested for their efficacy to sustain metal stress. Since the two bacterial strains (SBY and KY1) were able to grow in both medium with a potential to with stand higher metal concentration these strains were further studied. A metal tolerant magnetotactic bacterial strain Pseudomonas aeruginosa SBY was confirmed by TEM analysis to detect the accumulated metal within the cell. As bacterial strains were capable of tolerating higher concentration of metal, they may have a vital role in environmental bioremediation.