Streptococcus Pneumoniae is a gram positive, catalase negative, alpha-hemolytic bacteria that presents in lancet shaped coccus in pairs. Now there are many other organisms that have features that requires understanding their classification for memorizing for the USMLE Step 1. The question is how will you memorize them. It all comes down to understanding the basic foundation of Microbiology. I provided videos below which will make it easier to understand the basics of microbiology.
Introduction to Microbiology Part 1
Introduction to Microbiology Part 2
Bacteria Cell Wall Part 1
Bacteria Cell Wall Part 2
Bacteria Cell Wall Part 3
Endotoxins and Exotoxins