Lets have a look at this yeast.
Certainly by 1842 brewers and scientists knew that yeast was an important part of beer making (quite an advance from the days of The Reinheitsgebot where yeast is not even mentioned) though they were uncertain as to its function.
The renowned chemist of the time Justus von Liebig believed that fermentation was a chemical reaction triggered by the death and decomposition of yeast, whereas Theodore Schwann considered that fermentation was a living process involving the reproduction of yeast cells. It was not until Pasteur's experiments at the end of the 1870's that Schwann was shown to be correct.
The brewers did know that different breweries' yeast affected beer in different ways. In fact Sedlmayer and Dreher (more on them later) travelled around Europe and Britain around 1830 carrying a specially commissioned metal tube with a hidden valve with which they "stole" samples of fermenting wort, yeast and all.
The most probable answer to all this is that brewing practices in Northern Europe, particularly the British Isles, where the yeast was skimmed from the top of the ferment contrasted with the southern German practice which involved fermenting and lagering at low temperatures(beer was not made in the summer).
Thus we have two strains of yeast, one adapted to live well in warm, open conditions and another adapted to cold conditions, where the yeast would sink to the bottom during the storage period.
Fermentation, after all, occurs throughout the wort, not exclusively at the top or bottom !
The yeast used in Bavaria at the time was probably a mixed strain of S,Cerevisiae and S.Carlsbergensis (now S. Uvaram). S.Uvarum was first isolated as a single cell by Emil Hansen at the Carlsberg Brewery in Denmark in 1883.
The Carlsberg Brewery was founded by Jacob Jacobsen in 1847. Jacobsen had studied under Sedlmayer and it is believed that his yeast came from Sedlmayer's Spaten Brewery in Munich.