Concise answer:
All living organisms, including microbes, are made primarily of water, small molecules, and macromolecules. Each group serves different biological functions, and understanding them helps explain how disinfectants like peracetic acid interfere with microbes at the molecular level. Because PAA primarily targets macromolecules, knowing what those molecules are explains why PAA is effective at inactivating microbial life.
Longer, nuanced answer:
Microbes, like all forms of life, are composed of a structured mix of chemical substances that can be broadly categorized into water, small molecules, and macromolecules. Water acts as a solvent for transport and biochemical reactions and has unique physical properties that sustain life, such as floating when frozen. Small molecules include minerals, gases, vitamins, ATP, and precursors for biological polymers, all of which support cellular processes but are not the primary target of PAA.
Macromolecules—large biological polymers like polysaccharides, lipids, nucleic acids, and proteins—make up most of a cell’s structural and functional mass. These molecules are built from simpler repeating units, similar to assembling complex structures from LEGO bricks. They define the physiology, genetic identity, metabolism, and structural integrity of organisms.
PAA dissolves in water and influences acidity but does not significantly damage water or small molecules. Instead, its primary antimicrobial action occurs when it reacts with macromolecules such as proteins and nucleic acids, disrupting cellular function and causing microbial death or inactivation. Future explanations of PAA’s antimicrobial mechanism rely on this molecular foundation.
How does water support microbial life?
Concise answer:
Water dissolves nutrients and waste, enables chemical reactions, and stabilizes ecosystems by moderating temperature. Its unique property of becoming less dense when frozen helps preserve aquatic environments and microbial survival during cold seasons.
Longer answer:
Water acts as a solvent that transports essential molecules into and out of cells, participates directly in biochemical reactions, and influences environmental temperature stability. Unlike most substances, solid water floats rather than sinking, preventing lakes and oceans from freezing solid and allowing microbes to survive beneath ice layers. When PAA dissolves in water, it primarily changes pH rather than damaging water itself.
What are small molecules in living systems, and how do microbes use them?
Concise answer:
Small molecules include minerals, gases, vitamins, ATP, and building blocks of macromolecules. Microbes use them for metabolism, structural chemistry, and genetic functions, but these molecules are not PAA’s main target.
Longer answer:
Minerals such as calcium, magnesium, zinc, copper, and phosphorus support cell signaling, structure, and enzyme activity. Gases like oxygen, nitrogen, methane, and carbon dioxide are used by various microbes for respiration or as raw materials for metabolic processes. While these molecules can be altered chemically, their modification is not the primary mechanism by which PAA kills microbes, so the more important focus is macromolecular damage.
What are macromolecules, and why are they the primary targets of PAA?
Concise answer:
Macromolecules are large biological polymers like polysaccharides, lipids, nucleic acids, and proteins. Because these molecules are essential to cellular structure, genetics, metabolism, and function, disrupting them effectively neutralizes microbes.
Longer answer:
Macromolecules consist of long chains of repeating building blocks—amino acids form proteins, nucleotides form DNA and RNA, and sugars form polysaccharides. These structures define the physical and functional framework of organisms; for example, a single cell’s DNA can span six feet when fully stretched. PAA chemically attacks these large molecules through oxidation, damaging structures microbes need to replicate and survive. This molecular destruction is the key reason PAA serves as an effective disinfectant and will be discussed further in subsequent material.
— Dr. Matthew Crook