Microbiome positive or negative control (16S rRNA V3-V4)

How to employ a bacterial mock community, spike-in control, or negative control in microbiome sequencing. Which of these is in charge of contamination control in low-biomass sequencing? I've read a lot of publications, but I'm still confused about the technique for the mock community, spike-in control, and negative control. Can I use DNA elution buffer as a negative control? Is DNA-free water the negative control? I looked for the DNA of the bacterial strains to use as standards. I've seen the ATCC Microbiome standards as well as ZymoBIOMICS' mock community DNA standards. How can it be used for seminal plasma microbiome sequencing? The seminal microbiome has less biomass but a greater diversity of microbiomes than the vaginal microbiome.
Thank you in advance for your support!

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