The associations of microbes with their environment can result in both positive and negative effects on humans. While most people are aware of the existence of microbes, research shows that perceptions of microbes and their effects are often incomplete or include misconceptions. Much like the positive psychology movement, the recently proposed "positive microbiology" movement can help society to see microbes as tools to benefit mankind. The purpose of this study was to examine college students' knowledge and perception of the positive effects of microbes ("good" microbes) and the negative effects of microbes ("bad" microbes). College students in the United States (n = 924) were surveyed about their perceptions of the characteristics, effects, and responses to bacteria and viruses. Students viewed viruses more negatively than bacteria. For both bacteria and viruses, students struggled to provide examples of beneficial effects of microbes. Thus, we see the need for more instruction about the benefits of microbes. To this end, we offer practical suggestions for this instruction, including research about best practices for teaching and suggested plug-and-play resources available for instructors to incorporate the topic of positive microbiology into their courses.