'Simples' bactéria mostra complexidade surpreendente

sexta-feira, novembro 27, 2009

'Simple' bacterium shows surprising complexity

19:00 26 November 2009 by Andy Coghlan

The inner workings of a supposedly simple bacterial cell have turned out to be much more sophisticated than expected.

An in-depth "blueprint" of an apparently minimalist species has revealed details that challenge preconceptions about how genes operate. It also brings closer the day when it may be possible to create artificial life.

Anatomy of a bug: This “CT scan” shows the “bodily” positions of molecular motors vital to a Mycoplasma pneumoniae cell. They include ribosomes (yellow) for making proteins, chaperonins for folding them (red), RNA polymerases for “reading” genes and pyruvate dehydrogenase enzymes for producing energy (Image: Science)

Mycoplasma pneumoniae, which causes a form of pneumonia in people, has just 689 genes, compared with 25,000 in humans and 4000 or more in most other bacteria. Now a study of its inner workings has revealed that the bacterium has uncanny flexibility and sophistication, allowing it to react fast to changes in its diet and environment.

"There were a lot of surprises," says Peer Bork, joint head of the structural and computational biology unit at the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany. "Although it's a very tiny genome, it's much more complicated than we thought."

Master controllor

The biggest shock was that the organism gets by with just eight gene "switches", or transcription factors, compared with more than 50 in other bacteria such as Escherichia coli. Transcription factors are generally thought of as the key components enabling living things to respond to environmental conditions by switching genes on and off.

So how does the cell get by with so few "master controllers"? One possibility is that stretches of "antisense RNA" – basically genes copied back to front – stand in for the transcription factors as gene switches.

An even more intriguing possibility is that chemicals thought to serve as food – such as the sugar-like substance glycerol – are signalling messengers in their own right, helping to fine-tune what the cell does and how it reacts to changes in its environment.

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Qual teoria científica que preconiza a descoberta de 'surpreendentes' níveis de complexidade nas coisas bióticas? Design inteligente ou design não inteligente???