*3.2. E*ff*ect of S. aureus K1 Contact Time on Chromium (Cr6*+*) Reduction*

*Staphylococcus aureus* K1 exhibited optimum growth at pH 8 and 35 ◦C. Under optimum growth conditions, the effect of contact time on bacterial ability to reduce the hexavalent Cr in the medium was observed. It was observed that the Cr reduction of *S. aureus* K1 increased with increasing contact time (Figure 1). It was found that 26%, 45%, 71%, 80% and 99% Cr6<sup>+</sup> (initial metal concentration = 1 mM) was removed from the medium by *Staphylococcus aureus* K1 after 2, 4, 8, 16 and 24 h of incubation, respectively (Figure 1).

**Figure 1.** The impact of contact time (hours) impact on the Cr removal ability of *Staphylococcus aureus* K1.

#### *3.3. E*ff*ect of S. aureus K1 on Plant Growth Promotion*

Chromium stress substantially decreased the growth of wheat plants. A significant reduction in the length of shoots (31.18%), roots (32.02%) and spikes (40.70%) and the dry weight of shoots (34.29), roots (44.17) and grains (31.06%) of the plant was observed at 100 mg·kg−<sup>1</sup> Cr concentration alone as compared to *S. aureus* K1 inoculated seeds + 100 mg·kg−<sup>1</sup> Cr concentration (Figure 2). A significant change in shoot and root length was observed in inoculated plants as compared to uninoculated plants at all levels of Cr. Wheat plants stressed with 50 mg·kg−<sup>1</sup> of Cr showed an observable reduction in growth attributes; however, this decrease was minimized in inoculated plants compared to uninoculated plants, as shown in Figure 2. The growth was gradually decreased when the Cr concentration in the growth medium increased from 25 to 100 mg·kg−<sup>1</sup> (Figure 2A–D). Moreover, the maximum growth reduction was noticed with 100 mg·kg−<sup>1</sup> of Cr stress. The data regarding plant growth attributes

indicated that inoculation with *S. aureus* K1 significantly improved the wheat growth and dry biomass under Cr stress conditions.

**Figure 2.** Influence of the different Cr levels (0, 25, 50, 100 mg·kg<sup>−</sup>1), with and without peat-moss-based microbial inoculation, on length of shoot (**A**) and root (**B**), dry weight of shoot (**C**) and root (**D**) and grain dry weight (**E**) of wheat. Bars indicate the mean of three replicates with standard deviation (SD). Different bars with lowercase letters show noteworthy changes among various treatments at *p* < 0.05.
