Overview
Citrobacter freundii is a Gram-negative bacterium belonging to the Enterobacteriaceae family. It is widely distributed in nature, including in soil, water, and the gastrointestinal tracts of humans and animals. The bacterium is named after the German microbiologist Alfred Freund, who first described it. While often considered a commensal organism, C. freundii can act as an opportunistic pathogen, particularly in hospital settings. In industrial and research contexts, C. freundii is valued for its metabolic versatility. It can utilize citrate as a carbon source, which is a key diagnostic feature. The bacterium is also studied for its ability to produce enzymes like beta-lactamases, which have implications for antibiotic resistance research.
Physical and Chemical Properties
Citrobacter freundii is a rod-shaped, motile bacterium with peritrichous flagella. It is Gram-negative, meaning it has a thin peptidoglycan layer and an outer membrane containing lipopolysaccharides. The bacterium is facultatively anaerobic, capable of growing both in the presence and absence of oxygen. Biochemically, C. freundii is oxidase-negative and citrate-positive, which distinguishes it from other Enterobacteriaceae. It ferments glucose and other sugars, producing acid and gas. The bacterium can also reduce nitrate to nitrite, a trait useful for identification in laboratory settings.
Main Applications
In industrial microbiology, Citrobacter freundii is used for the production of enzymes such as penicillin acylase, which is important for synthesizing semi-synthetic antibiotics. The bacterium's ability to degrade complex organic compounds makes it useful in bioremediation and wastewater treatment. In clinical and research settings, C. freundii is studied for its role in nosocomial infections and antibiotic resistance. Some strains harbor plasmids encoding resistance genes, making them a focus of studies on horizontal gene transfer. The bacterium is also used as a model organism in microbial genetics and biochemistry research.
Safety and Storage
Citrobacter freundii is classified as a Biosafety Level 2 (BSL-2) organism due to its potential to cause infections, particularly in immunocompromised individuals. Laboratory handling requires standard microbiological practices, including the use of personal protective equipment (PPE) and proper disinfection protocols. For long-term storage, C. freundii cultures are typically preserved at -80°C in glycerol stocks or as lyophilized (freeze-dried) samples. Working cultures can be maintained on agar plates or in liquid media at 4°C for short-term use, with regular subculturing to ensure viability.
B2B Procurement Guide
When procuring Citrobacter freundii strains for industrial or research purposes, it is essential to verify the strain's authenticity and intended application. Reputable suppliers should provide detailed information on the strain's origin, growth conditions, and any genetic modifications. Pricing varies depending on the strain's characteristics and the supplier's offerings. For reference, lyophilized cultures or glycerol stocks may range from $50 to $200 per strain. Bulk purchases for industrial applications may qualify for discounts. Always confirm shipping and storage requirements to ensure viability upon arrival.