gram neagtive bacilli on slide

bacilli bacillus bacteria bacterial bacteriology bacterium biology cells colony contagion contagious contamination disease epidemic epidemiology experiment flora germ germs gut health healthy human hygiene immune infected infection intestinal isolated lactobacillus medicine microbe microbiology microbiome microbiota microorganism microscopic outbreak pandemic pathogen pathogenic pathogens probiotic research rod salmonella science sickness system virus