Final answer:
The growth of bacteria is significantly affected by the amount of moisture; most bacteria require high water activity to thrive, while some forms of fungi and halotolerant pathogens can tolerate less moisture or high osmotic pressures.
Step-by-step explanation:
Yes, the amount of moisture available does impact the growth of bacteria. Bacterial growth is closely related to the concept of water activity (aw), which is a measure of the available moisture in a medium.
This moisture can be affected by the inherent water content of the material or by the presence of solute molecules like salts and sugars.
A high water activity (aw), typically ranging from 0.97 to 0.99, is required for most bacteria to grow optimally. In contrast, fungi can grow at lower aw levels, around 0.8 to 0.75.
The preservation of food often involves reducing water activity through drying, freeze-drying, or adding high concentrations of salts or sugars to increase osmotic pressure and create an environment inhospitable to microbes.
Pathogens known as halotolerant can still cause foodborne illnesses as they can tolerate high salt environments used in food preservation.
Some bacteria also have special requirements, such as photosynthetic bacteria that rely on light for energy. Conversely, other microorganisms have adapted to grow in dry or high osmotic pressure environments, but most require more favorable, moist conditions to thrive.