Can bacteria cause lower respiratory tract infections?

Yes: Bronchitis and pneumonia can be caused by many viruses, many bacteria, and all the same infectious agents that can cause one person a simple cold, sore throat, ear or sinus infection, may cause another person bronchitis, or pneumonia.

Yes: There are several types: streptococcus pneumoniae, staphylococcus aureus, atypical bacteria such as chlamydophila pneumoniae, mycoplasma pneumoniae, and legionella pneumophila. Also sometimes haemophilus influenzae, klebsiella pneumoniae, escherichia coli, pseudomonas aeruginosa and moraxella catarrhalis.