## 3 Results and Discussion
### Metallic Nanoparticle Synthesis by M. magnetotacticum Using Either Fe, Ag, Au or Zn
#### 3.2.2 DLS Analysis  
Dynamic light scattering (DLS) was used to determine the hydrodynamic sizes of the metallic nanoparticles synthesized. Table 4 shows all the DLS size ranges (nm) and TEM size ranges (nm) obtained for the metallic nanoparticles that were verified using EDX analysis. It should be noted that the sizes obtained using Image J software for TEM analysis were much smaller when compared to the sizes obtained via DLS which is due to TEM  
Figure 5: (**A**,**B**) TEM micrographs showing silver-containing magnetosomes formed by _M. magnetotacticum_ after incubation at 30\({}^{\circ}\) for 48 h in MSGM 9 (sodium nitrate and Isogro(tm) containing silver (10 mM). Nanoparticles have a width of 2–42 nm and length of 32–59 nm. (**C**) EDX profile of the observed nanoparticles presented in (**A**). Distinct silver peaks are present confirming presence of silver-containing nanoparticles. Samples were analysed using carbon-coated copper grids and therefore high peaks denoting carbon and copper are also present. The other peaks present are due to medium components and elements present as part of normal bacterial composition. being a number-based particle size measurement whereas DLS is an intensity-based one. Therefore, DLS is very sensitive to the large particles as they were highly agglomerated and thus puts higher emphasis on the larger particle sizes whereas TEM shows stronger emphasis on the smallest components in the size distribution. This can be attributed to the difference in nature of the samples being analysed as the samples analysed via DLS were suspended in an aqueous solution which could have caused the nanoparticles to aggregate accounting for the larger sizes. The significant difference between the hydrodynamic sizes and the TEM sizes could be explained by the formation of a hydration shell on the surface of the particles present in water, which significantly affects the dynamic light scattering measurements as explained by [PERSON] et al. (2018) [46]. The size range obtained for iron-containing nanoparticles using DLS was 24-68 nm for MSGM original; however, a peak with a size range of 712-6439 nm was also present and could be attributed to the high degree of agglomeration (Figure 6). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**MSGM Modification**} & \multirow{2}{*}{**Metal**} & \multicolumn{2}{c}{**Size (nm)**} & \multicolumn{2}{c}{**Zeta Potential (mV)**} & \multirow{2}{*}{**PDI Values**} \\ \cline{3-3} \cline{5-6}  & & **DLS** & **TEM** & & **and Stability** & \\ \hline \multirow{3}{*}{MSGM original} & Fe & 24–68 nm & 6–7 nm & \(-\)26 (incipient instability) & 0.534 (mid-range polydispersity) \\ \cline{2-6}  & Ag & - & - & - & - \\ \cline{2-6}  & Au & 66–195 nm & Agglomerated & \(-\)35 (moderate stability) & 0.601 (mid-range polydispersity) \\ \hline \multirow{3}{*}{MSGM 6 (sodium nitrate)} & Fe & 149–199 nm & Agglomerated & \(-\)40 (good stability) & 0.368 (mid-range polydispersity) \\ \cline{2-6}  & Ag & - & - & - & - \\ \cline{2-6}  & Au & 599–705 nm & Agglomerated & \(-\)23 (incipient instability) & 0.574 (mid-range polydispersity) \\ \hline \multirow{3}{*}{MSGM 9 (sodium nitrate and Isogro\({}^{\text{TM}}\))} & Fe & 74–239 nm & 4–6 nm & \(-\)44 (good stability) & 0.411 (mid-range polydispersity) \\ \cline{2-6}  & Ag & 154–187 nm & 2–59 nm & \(-\)40 (good stability) & 0.541 (mid-range polydispersity) \\ \cline{1-1} \cline{2-6}  & Au & 270–284 nm & Agglomerated & \(-\)15 (incipient instability) & 0.361 (mid-range polydispersity) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Size and zeta potential obtained for each metal (Fe, Ag and Au) synthesized using MSGM original, MSGM 6 (sodium nitrate) and MSGM 9 (sodium nitrate and Isogro\({}^{\text{TM}}\)). Figure 6: Size distribution intensity from DLS analysis of iron-containing magnetosomes formed by _M. magnetotacticum_ after incubation at 30\({}^{\circ}\) for 48 h in MSGM original containing iron (10 mM).