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The vaccines currently available for anthrax and botulism are far from ideal; therefore, harnessing the potential of probiotic lactobacilli for delivery of mucosal antigens against these diseases holds promise. O'Flaherty and Klaenhammer (p. 6091–6101) constructed a novel strain of Lactobacillus acidophilus to express both antigens from the chromosome downstream of a highly expressed glycolytic pathway gene. This precise insertion of antigen-encoding genes in the L. acidophilus genome negates the need for plasmid expression and demonstrates that engineered high-level expression from a single location in the chromosome is more stable than and as efficient as expression from a multicopy plasmid.
Microbial nitrate-reducing Fe(II) oxidation couples the three important element cycles of iron, nitrogen, and carbon. However, to date, it is still unclear whether or to what extent Fe(II) oxidation coupled to nitrate reduction is an enzymatically catalyzed and energy-yielding autotrophic process or whether Fe(II) is abiotically oxidized by nitrite from heterotrophic nitrate reduction. Laufer et al. (p. 6120–6131) now provide evidence for the existence of autotrophic nitrate-reducing Fe(II) oxidizers in coastal marine sediments through 14C-amended microcosm experiments. This discovery now allows identification of the responsible microorganisms in such sediments.
The production of biodegradable polymers from inexpensive and abundant feedstocks is aimed at contributing to an environment-friendly and sustainable future plastics industry economy. Synthesis gas (syngas) accrues as a waste gas from industrial processes or through pyrolysis of organic residues not competing with human nutrition. Heinrich et al. (p. 6132–6140) genetically engineered the purple bacterium Rhodospirillum rubrum to synthesize so-called medium-chain-length polyhydroxyalkanoates (PHAs) with rubber-like, advantageous material properties from carbon monoxide- and carbon dioxide-containing syngas. So far, the microbial synthesis of PHAs from this feedstock has been limited to stiff and brittle short-chain-length PHAs; this study extends the possible applications of syngas-derived biopolymers to elastomeric PHAs.
There are limited data on microbial populations present in smokeless tobacco products used by U.S. consumers. Han and colleagues (p. 6273–6283) examined various smokeless tobacco product types and identified multiple bacterial species that are of possible concern due to their potential to cause opportunistic infections or contribute to the formation of carcinogenic tobacco-specific N′-nitrosamines. Overall, this study provides a microbiological baseline to help fill knowledge gaps related to the microbiological risks of smokeless tobacco products.
A peptidoglycan (PG) layer resides in the periplasmic spaces of Gram-negative bacteria. The importance of PG acetylation in Gram-negative bacteria has not been fully elucidated. Iwata et al. (p. 6284–6290) reported that reduced PG acetylation causes decreased motility of and biofilm formation by Campylobacter jejuni, thus leading to a deficiency in chicken intestine colonization by this Gram-negative bacterium. C. jejuni is a predominant cause of foodborne illness worldwide, and the chicken is considered to be the main reservoir of this pathogen. Inhibitors of the PG acetylation enzymes might serve as potent anti-C. jejuni agents to prevent colonization in the chicken intestine.