Construction of a model secretion system for oral streptococci

Area of Science:

• Microbiology
• Molecular Biology
• Biotechnology

Background:

• Streptococcus mutans produces glucosyltransferases involved in dental plaque formation.
• Alpha-amylase is an enzyme that breaks down starch.
• Genetic engineering allows for the creation of hybrid genes to study protein secretion.

Purpose of the Study:

• To construct and express a hybrid gene encoding a signal peptide from Streptococcus mutans and alpha-amylase from Bacillus sp. in oral streptococci.
• To investigate the efficiency of extracellular amylase production in different Streptococcus species using this hybrid gene.

Main Methods:

• A hybrid gene was created by fusing the secretory domain of the Streptococcus mutans GS-5 gtfB gene with the alpha-amylase gene from Bacillus sp.
• This hybrid gene was inserted into a Streptococcus-E. coli shuttle vector.
• The shuttle vector was transformed into Streptococcus gordonii, Streptococcus mutans, and Streptococcus milleri.

Main Results:

• Streptococcus gordonii transformed with the hybrid gene showed high extracellular amylase production.
• Transformants with the intact amylase gene exhibited only minimal amylase activity.
• Streptococcus mutans and Streptococcus milleri transformants displayed weak amylase activity, indicating secretion inefficiencies.

Conclusions:

• Streptococcus gordonii can efficiently secrete hybrid amylase using the Streptococcus mutans signal peptide.
• The inability of Streptococcus mutans and Streptococcus milleri to secrete hybrid amylase suggests issues with their host secretory machinery.
• This study highlights the potential of using heterologous signal peptides for enhanced protein secretion in specific bacterial hosts.