Frontiers in Microbiology remediate heavy metals, but the use of microorganisms is cheap, less

Overview

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with 70% ethanol for 2 min. After draining the ethanol solution,
Furthermore, soybean is among the most affordable and Cr+6 (i.e., 100, 300, 500, 900, or 1,200 ppm) in the form of
Screening experiment fungal culture supernatant (0.5 ml), 10% aluminum chloride
(0.1 ml), 10% potassium acetate (0.1 ml), and 80% methanol
were applied in the form of fungal spore suspension at the chloride (10%), 0.1 ml of potassium acetate (10%), and 4.8 ml
rate of 10−8 . The plants were kept in the growth chamber for of methanol (80%). Quercetin was used as a standard.
Profiling of fungal culture filtrate 5 min. After 5 min, 2 ml of sodium carbonate (20%) solution
100, 300, 500, 900, or 1,200 ppm) in 250 ml flasks. After at 765 nm against the blank. The blank solution was prepared by
of Salkowski’s reagent (50 ml of 35% perchloric acid, 1 ml of 0.5
chloride (0.1%) solution was added to it. A violet color was
tolerant isolates were selected to conduct the pot experiment in were crushed in 4 ml of sulfosalicylic acid solution (3%) and the
with 0.1% HgCl2 and washed three times with sterile distilled of the leaves’ supernatant was mixed with acid ninhydrin reagent
inoculation and Cr concentrations (i.e., 0, 10, and 50 ppm).
humidity was not regulated and ranged from 50 to 80%, and mixture was centrifuged for 10 min at 504 × g. Supernatant
frozen in liquid nitrogen) and stored at –80◦ C till growth, and sodium potassium tartrate (0.5 ml) and 2% sodium carbonate in
biomass was crushed in 5 ml of 80% ethanol and the suspension
supernatant, 1 ml of 80% phenol was added and the mixture was
Fresh soybean leaves (0.5 g) were crushed in 5 ml of 80%
Determination of proline tube were shaken vigorously, 0.8 ml of 0.73% NaCl was added
The %DPPH free-radical scavenging activity in soybean for 16 h at 25–30◦ C. Centrifugation was done at 504 × g and
(2001) using 0.004% solution of DPPH as a source of free radical. the obtained residue from the Step 2 was treated with 5 ml of
Changes in absorbance were measured at 517 nm against the 30% H2 O2 and the contents were shaken for 1 h. This step was
the analysis of variance (ANOVA) and Duncan’s Multiple Range with 300 (71 µg/ml), 600 (75 µg/ml), 900 (75 µg/ml), or
Test (DMRT) were conducted to establish the significance level 1,200 (67 µg/ml) ppm of Cr in comparison to the 0 ppm Cr
Results media of S. lycopersici supplemented with 0 ppm of Cr was 130
Figure 4B). However, in the presence of 1,200 ppm Cr in culture
of tolerating Cr stress up to 1,200 ppm (Supplementary
Table 1). From the preliminary screening, the most effective Effect of Cr on flavonoids and
1,200 ppm significantly (p < 0.05) increased by 26.56 µg/ml as
and Cp2 supplemented within 0 ppm Cr (Supplementary Figure 4B).
maximum homology (100%) with Stemphylium lycopersici and (p < 0.05) decrease in the phenolic contents with increasing Cr
Cp2 showed (92%) homology with Stemphylium solani. Isolate concentration (100–1,200 ppm) in the culture media. In case
supported by 96 and 100% bootstrap value in the consensus tree noticed at 300 and 600 ppm of Cr, which increased significantly
(Supplementary Figure 3). Combine results of phylogenetic (p < 0.05) at 1,200 ppm of Cr (Supplementary Figure 4D).
Exposing plants to 10 or 50 ppm of Cr stress significantly
S. lycopersici culture supernatant spiked with 100, 300, 600, 900, not affected (p < 0.05), when exposed to 10 ppm of Cr stress.
or 1,200 ppm of Cr was 20, 18, 18, 19, and 18 µg/ml, respectively However, at 50 ppm of Cr stress, the reduction in shoot lengths
higher concentration of IAA (88 µg/ml) was observed in the reduced by 13.6 and 16.1% (Figure 1A). The root lengths of
isolate S. solani under 100 ppm Cr stress as compared to the endophytes-free soybean plant were significantly (p < 0.05)
Cp1 = Stemphylium lycopersici; Cp2 = Stemphylium solani; Ctrl = control; Cr1 = 10 ppm chromium; Cr2 = 50 ppm chromium. Each bar
represents mean of triplicated data (n = 3) with standard error. Bars that are labeled with different letters are significantly different at p < 0.05
reduced by 60.5 and 57% at 10 and 50 ppm of chromate soybean plants were significantly higher than their respective

Methods (brief)

can cause oxidative stress. The oxidative stress further inhibits the plant C. comosum was carefully collected in plastic bags. The
seed germination and seedling development, reduces root shoot collected plant specimens were brought to the Plant-Microbe
in tap water. For surface sterilization, the samples were cut
plants (Redman et al., 2011). Fungal endophytes possess a well- final wash were also plated on Hegam agar media. Pure isolates
collected supernatant was then tested for IAA, Salicylic acid Taxonomic characterization
Fungal culture supernatant was carefully collected and
Hoagland’s solution. Each pot of 450 ml capacity received 400 ml was boiled at 100◦ C for an hour. The samples were left to cool
treatments were factorial combinations of two factors: fungal 520 nm. Toluene without a sample was used as a blank.
spore ml−1 using a hemocytometer. The spore suspension Total protein concentration in samples was determined by
5 min. The supernatant was carefully collected and quantified
sample was ground in chloroform: methanol (2:1 v/v), and the
proline contents in the leaves of the soybean. Fresh leaves (0.1 g) was separated/collected through the separatory funnel. After
sample was then cooled and 2.4 ml of vanillin reagent was added.
fractions. To 0.5 g of air-dried samples, 20 ml of 0.11 M acetic
shaking incubator for 12–24 h at 25–30◦ C. The samples were
samples using guaiacol as a source of reactive oxygen species
and 0.1 ml plant extract. POD activity in the samples was
sample. To the dried sample, 25 ml of 1 M ammonium acetate

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Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.

Commit	Date	Change	Description
b01ec52c	2026-08-04	major	2 sections added
d49e450f	2026-08-03	major	5 sections added; narrative text revised