The study identifies 382 essential protein-coding genes and 43 RNA-coding genes in Mycoplasma genitalium, a bacterium with the smallest genome of any organism that can be grown in pure culture. Using global transposon mutagenesis, researchers isolated and characterized gene disruption mutants for 100 nonessential protein-coding genes. None of the 43 RNA-coding genes were disrupted, suggesting they are essential. The study found that 28% of the essential protein-coding genes encode proteins of unknown function. Disruption of some genes accelerated M. genitalium growth. The study also identified five sets of disrupted genes that encode proteins with potentially redundant essential functions, such as phosphate transport. The results suggest that M. genitalium is close to being a minimal bacterial cell due to its lack of genomic redundancy and contingencies for different environmental conditions. The study also found that some genes may be nonessential but their products may perform essential biological functions. The study highlights the importance of gene essentiality studies in bacteria with near minimal genomes to verify the compositions of hypothetical minimal gene sets. The study also found that some genes may be essential but their functions are not yet fully understood. The study concludes that the essential gene set for M. genitalium includes 382 protein-coding genes, 3 phosphate transporter genes, and 43 RNA-coding genes. The study also expands the projection of the set of essential genes to 387 to include two paralogous gene families. The study suggests that a genome constructed to encode 387 protein-coding and 43 structural RNA genes could sustain a viable synthetic cell. The study also highlights the importance of gene synthesis technology and genome transplantation methods in determining the minimal set of genes needed to support cellular growth.The study identifies 382 essential protein-coding genes and 43 RNA-coding genes in Mycoplasma genitalium, a bacterium with the smallest genome of any organism that can be grown in pure culture. Using global transposon mutagenesis, researchers isolated and characterized gene disruption mutants for 100 nonessential protein-coding genes. None of the 43 RNA-coding genes were disrupted, suggesting they are essential. The study found that 28% of the essential protein-coding genes encode proteins of unknown function. Disruption of some genes accelerated M. genitalium growth. The study also identified five sets of disrupted genes that encode proteins with potentially redundant essential functions, such as phosphate transport. The results suggest that M. genitalium is close to being a minimal bacterial cell due to its lack of genomic redundancy and contingencies for different environmental conditions. The study also found that some genes may be nonessential but their products may perform essential biological functions. The study highlights the importance of gene essentiality studies in bacteria with near minimal genomes to verify the compositions of hypothetical minimal gene sets. The study also found that some genes may be essential but their functions are not yet fully understood. The study concludes that the essential gene set for M. genitalium includes 382 protein-coding genes, 3 phosphate transporter genes, and 43 RNA-coding genes. The study also expands the projection of the set of essential genes to 387 to include two paralogous gene families. The study suggests that a genome constructed to encode 387 protein-coding and 43 structural RNA genes could sustain a viable synthetic cell. The study also highlights the importance of gene synthesis technology and genome transplantation methods in determining the minimal set of genes needed to support cellular growth.