Marmite has become synonymous for anything some people love and other people hate. Anything with a high salt content and rich in 'Umami' could be used as a replacement. The Greeks and Romans had Garum which I assume did very much the same job as Marmite but was a bit more universally loved perhaps.

Salmonella sounds good. It definitely looks more than a couple of steps up from a cold tomato cupasoup.

(I've just been spellchecking this and the spellchecker underlined Salmorejo and suggested 'Salmonella'!)