New nano-weapon discovered in use by antibiotic-resistant hospital superbugs to kill off competing bacteria

Amazing stuff! Good news!

"A. baumannii bacteria is a nasty antibiotic-resistant bug that thrives in hospitals ... an opportunistic bacteria ... often found on the skin of healthcare workers, which makes it highly transmissible. ...

it can outcompete other bacteria in its environment. Focussing on that, the team discovered that the bacteria wipes out the competition by using a needle-like nano "machine" that injects deadly toxins into nearby bacteria.

"We learned how this toxin, called Tse15, is attached to the needle and then delivered into other bacteria to kill them," ..."

"... that bacteria rarely exist alone; like plants and animals, different types compete for space and resources. “In many environments, A. baumannii must engage in bacterial ‘warfare’ to survive in the presence of other species,” ...

“To outcompete surrounding bacteria, A. baumannii (and many other bacteria) use a nano-weapon called the Type VI Secretion System (T6SS). This is a tiny needle-like machine that injects toxins directly into nearby bacteria, killing them so that A. baumannii can dominate.” ..."

From the abstract:

"The type VI secretion system (T6SS) is a molecular machine utilised by many Gram-negative bacteria to deliver antibacterial toxins into adjacent cells. Here we present the structure of Tse15, a T6SS Rhs effector from the nosocomial pathogen Acinetobacter baumannii. Tse15 forms a triple layered β-cocoon Rhs domain with an N-terminal α-helical clade domain and an unfolded C-terminal toxin domain inside the Rhs cage. Tse15 is cleaved into three domains, through independent auto-cleavage events involving aspartyl protease activity for toxin self-cleavage and a nucleophilic glutamic acid for N-terminal clade cleavage. Proteomic analyses identified that significantly more peptides from the N-terminal clade and toxin domains were secreted than from the Rhs cage, suggesting toxin delivery often occurs without the cage. We propose the clade domain acts as an internal chaperone to mediate toxin tethering to the T6SS machinery. Conservation of the clade domain in other Gram-negative bacteria suggests this may be a common mechanism for delivery."

New nano-weapon discovered in use by menacing bacteria

Discovery boosts fight against antibiotic-resistant hospital superbugs

Structure of a Rhs effector clade domain provides mechanistic insights into type VI secretion system toxin delivery (open access)

Fig. 7: Delivery schematic for Tse15:VgrG15.