Jaagni Parnami

De­grad­a­tion of the mar­ine red algal poly­sac­char­ide car­rageenan by hu­man gut bac­teria

Algal poly­sac­char­ides in the mar­ine en­vir­on­ment provide car­bon for mi­crobes that can scav­enge these mo­lecules with spe­cial­ized pro­tein path­ways. These poly­sac­char­ide de­grad­a­tion path­ways are of­ten not re­stric­ted to one eco­sys­tem but rather ex­changed via ho­ri­zontal gene trans­fer. This al­lows bac­teria from dif­fer­ent en­vir­on­ments to ex­pand their abil­ity to con­sume new poly­sac­char­ides. Hu­man gut bac­teria have sim­il­arly evolved by gene trans­fer to de­grade mar­ine algal poly­sac­char­ides such as por­phyran, agar and al­gin­ate. An­other red algal poly­sac­char­ide ‘Car­rageen­an’ is a re­l­at­ively re­cent ad­di­tion in the West­ern­er’s diet. It is used ex­tens­ively by the food in­dustry as an emul­si­fy­ing agent but it re­mained un­known whether the gut bac­teria could meta­bol­ize this poly­sac­char­ide.

My PhD pro­ject fo­cuses on a hu­man gut bac­terium that has evolved to spe­cific­ally cap­ture, cata­bol­ize and con­sume car­rageenan us­ing a multi-pro­tein mem­brane sys­tem. Since this de­grad­a­tion path­way stems from mar­ine bac­teria, the bio­chem­ical and mi­cro­bial mech­an­ism of car­rageenan de­grad­a­tion in the gut eco­sys­tem con­trib­utes to the un­der­stand­ing of or­ganic mat­ter de­grad­a­tion in the sea